Tuberculosis (TB) remains a major global public health concern and continues to impose a substantial burden of morbidity, mortality, and socioeconomic consequences, particularly in low- and middle-income countries. Despite advances in molecular diagnostics, effective anti-tuberculosis treatment, and public health interventions, sustained transmission of Mycobacterium tuberculosis remains a significant obstacle to global TB elimination. India accounts for a substantial proportion of the global TB burden, making early case detection, interruption of transmission, and prevention of progression from TB infection to active disease essential components of national control strategies [1,2]. Household contacts of individuals with pulmonary TB constitute an especially vulnerable population because of repeated and prolonged exposure to infectious respiratory aerosols within shared living environments. The probability of infection and subsequent disease progression is influenced by several factors, including the infectiousness of the index case, duration and intensity of exposure, household overcrowding, ventilation, nutritional status, age, and underlying immunosuppression. Young children, particularly those younger than five years, and immunocompromised individuals are at increased risk of developing active TB following infection. Consequently, systematic household-contact investigation represents an important intervention for identifying previously undiagnosed TB, detecting TB infection, and providing preventive treatment to eligible individuals [3,4]. Household-contact investigation generally involves identification and enumeration of contacts, systematic screening for symptoms suggestive of TB, clinical and radiological assessment, microbiological confirmation when indicated, and evaluation for tuberculosis preventive treatment (TPT). Various screening approaches have been employed, ranging from symptom-based screening to integrated algorithms incorporating chest radiography, sputum microscopy, mycobacterial culture, and rapid molecular diagnostic tests such as Xpert MTB/RIF. Although symptom screening is inexpensive and operationally feasible in community settings, its sensitivity may be insufficient for detecting individuals with asymptomatic or subclinical disease. Incorporating chest radiography and appropriate microbiological investigations may improve diagnostic ascertainment, particularly among high-risk contacts and individuals exposed to drug-resistant TB [3,5]. The World Health Organization (WHO) recognizes household contacts of patients with bacteriologically confirmed pulmonary TB as a priority population for systematic screening and preventive interventions. Current WHO guidance strongly recommends TPT for children younger than five years after active TB disease has been excluded, even when testing for TB infection is unavailable. Preventive treatment may also be offered to older children, adolescents, and adults following appropriate clinical evaluation. Recommended preventive-treatment options include isoniazid-based and rifamycin-containing regimens, with regimen selection guided by age, drug susceptibility, comorbidities, contraindications, and relevant national recommendations [3,6]. In India, the National Tuberculosis Elimination Programme (NTEP) has progressively strengthened household-contact investigation and expanded the implementation of TPT as part of its comprehensive TB prevention strategy. The Guidelines for Programmatic Management of Tuberculosis Preventive Treatment in India provide a framework for systematic contact identification, exclusion of active TB disease, assessment of preventive-treatment eligibility, treatment initiation, adherence support, adverse-event monitoring, and documentation of treatment outcomes. These measures aim to complement early diagnosis and effective treatment of active TB by reducing the risk of future disease among vulnerable household contacts [2,7]. Nevertheless, translating these recommendations into routine healthcare practice remains challenging. Implementation of household-contact screening and preventive treatment requires coordination across multiple stages of care, beginning with contact identification and extending through diagnostic evaluation, eligibility assessment, treatment initiation, and completion. Interruptions at any stage may compromise overall programme effectiveness. In resource-constrained settings, inadequate contact enumeration, limited diagnostic access, delays in household visits, insufficient counselling, treatment-related concerns, migration, and incomplete follow-up may contribute to missed opportunities for TB prevention. Evidence from Indian studies has demonstrated considerable variation in household-contact screening coverage, active TB detection, TB infection prevalence, and preventive-treatment outcomes. Some community-based investigations have reported substantial yields of previously undiagnosed active TB, whereas programme-based evaluations have identified important differences in TPT initiation and completion. Furthermore, improvements in initial screening coverage do not necessarily translate into proportionate improvements in preventive-treatment delivery. These observations underscore the importance of examining the entire household-contact management pathway rather than evaluating individual screening or treatment indicators in isolation. Recent expansion of preventive-treatment services, greater availability of rapid diagnostic technologies, and the introduction of shorter TPT regimens have created additional opportunities to improve household-contact management in India. However, differences in study populations, diagnostic algorithms, TPT eligibility criteria, programme settings, and outcome definitions complicate the interpretation and comparison of existing evidence. An integrated synthesis is therefore needed to identify common implementation gaps, examine variations in programme performance, and determine strategies that may strengthen household-contact screening and preventive-treatment delivery. The present systematic review aims to synthesize available evidence from India regarding household-contact screening strategies, the yield of active TB detection, tuberculosis infection assessment, and implementation of preventive treatment. Specifically, the review evaluates screening coverage, diagnostic approaches, TPT eligibility, treatment initiation and completion, factors associated with programme performance, and barriers affecting progression through the preventive-treatment care cascade. By integrating clinical, epidemiological, and programmatic findings, this review seeks to inform evidence-based approaches for strengthening household-contact investigation and TB prevention under NTEP.

Eligibility and outcomes Eligible designs included observational and intervention studies with separately extractable Indian household-contact data. No publication-date cutoff was imposed as an eligibility criterion. The last literature search was conducted on 31 January 2026. Primary outcomes were active TB detection and TPT initiation and completion; secondary outcomes included screening coverage, infection-test positivity, timeliness, barriers and data completeness. 2.2. Information sources and reproducible strategy Literature sources considered were MEDLINE/PubMed, Embase, Scopus, Web of Science and the Cochrane Library, supplemented by citation and reference checking. The last literature search was conducted on 31 January 2026. The example PubMed search logic was: (tuberculosis OR TB) AND ("household contact" OR "contact tracing") AND (screening OR "active case finding" OR "preventive treatment" OR TPT) AND India. No publication-date restriction was specified as an inclusion or exclusion criterion. 2.3. Selection, data extraction and synthesis The study-selection framework included identification, deduplication, title/abstract screening, full-text eligibility assessment and extraction of study setting/design, contacts identified and screened, diagnostic strategy, TB yield, infection testing and TPT stages. Descriptive comparisons preserved the original denominators; no pooled estimate was calculated because of population and outcome heterogeneity. 2.4. Bias and certainty assessments Methodological concerns were considered across participant selection, exposure and outcome measurement, and missing data, with design-appropriate JBI and ROBINS-I domains providing the assessment framework. Table 9 presents the study-level methodological concern categories. Certainty was not graded because outcomes and designs were too heterogeneous for a pooled estimate.

Table 1. Prespecified inclusion and exclusion criteria Domain Inclusion criteria Exclusion criteria Population Household contacts of diagnosed TB patients Non-household contacts without disaggregated data Geography India or extractable India subgroup Outside India without India-specific results Design Original observational, interventional and mixed-methods research Editorials, reviews, duplicate publications Interventions Contact screening, case finding, TB infection testing or TPT No relevant household-contact pathway Outcomes Active TB, infection, screening/TPT cascade or implementation barriers No extractable relevant outcome Language English-language reports in this review scope Unavailable English-language material 3.1. Study selection The evidence synthesis comprised 26 primary studies investigating tuberculosis screening strategies, active case detection, tuberculosis infection, and preventive treatment implementation among household contacts in India. The studies were identified through electronic database searching and supplementary reference screening, with the last literature search conducted on 31 January 2026. Figure 1 presents the PRISMA 2020 study-selection schematic, and the characteristics of the 26 studies are summarized in Table 2. 3.2. Characteristics of the Included Evidence A total of 26 primary studies published between 2009 and January 2026 were identified for the evidence synthesis. The studies represented diverse geographical regions of India, including Tamil Nadu, Delhi, Karnataka, Maharashtra, Madhya Pradesh, West Bengal, Chhattisgarh, Andhra Pradesh, Telangana, and Uttar Pradesh. Both urban and rural populations were represented, reflecting variations in healthcare accessibility, tuberculosis burden, and implementation of household-contact investigation and preventive-treatment services. The included studies employed heterogeneous methodological designs, comprising prospective cohort studies, retrospective record-based investigations, community-based cross-sectional surveys, contact-screening interventions, mixed-methods evaluations, and analyses of routinely collected programme data. Study populations ranged from small cohorts of child household contacts to large-scale programme evaluations involving more than 400,000 contacts. Participants included children, adolescents, and adults exposed to patients with pulmonary tuberculosis, including contacts of individuals with multidrug-resistant tuberculosis. The screening approaches varied considerably and included symptom-based assessment, chest radiography, sputum smear microscopy, mycobacterial culture, Xpert MTB/RIF, tuberculin skin testing, and interferon-gamma release assays. Earlier studies primarily focused on active tuberculosis detection, childhood contact investigation, and implementation of isoniazid preventive therapy. More recent investigations evaluated expanded tuberculosis preventive treatment (TPT) eligibility, infection-testing strategies, shorter preventive-treatment regimens, treatment initiation and completion, and attrition across successive stages of the household-contact management cascade. The reported outcomes included household-contact identification and screening coverage, active tuberculosis detection yield, tuberculosis infection prevalence, TPT eligibility, treatment initiation, adherence, completion, timeliness of service delivery, and operational barriers. Considerable variation was observed in study populations, diagnostic algorithms, preventive-treatment approaches, and outcome definitions, highlighting differences in programme implementation across Indian settings. The detailed characteristics, study populations, screening and preventive-treatment strategies, and principal findings of the 26 primary studies are summarized in Table 2. Table 2. Characteristics of Identified Primary Studies Evaluating Tuberculosis Screening Strategies and Preventive Treatment Implementation Among Household Contacts in India No. Study (year) Study setting Study design Study population and sample size Screening/TPT strategy Principal findings 1 Contact screening and chemoprophylaxis situational analysis (2009) Chennai and Vellore, Tamil Nadu Cross-sectional programme evaluation 253 pulmonary TB index patients; 220 child contacts Contact identification, child-contact screening and IPT Only 31/220 (14%) children were screened; 16/84 (19%) children younger than six years initiated IPT. 2 South Indian district contact-screening study (2011) Krishna district, Andhra Pradesh Cross-sectional operational study 848 index patients; 172 child contacts younger than six years Household visits, TB screening and IPT provision 116/172 (67%) children evaluated; 97/116 (84%) evaluated children initiated IPT. 3 Rekha et al. (2013) South India Prospective pilot intervention 87 household child contacts younger than six years IPT register, contact cards and healthcare-worker training 71/87 (82%) contacts traced; 53 screened and initiated on IPT; 39 completed treatment. 4 Singh et al. (2013) South Delhi Prospective household cohort 432 index cases; 1,608 household contacts Clinical assessment, sputum culture and longitudinal follow-up Of 1,206 contacts providing sputum, 83 (6.9%) were culture-positive; 52 co-prevalent and 31 incident TB cases identified. 5 Isoniazid preventive treatment in two Tamil Nadu districts (2014) Tamil Nadu Household-based observational study 691 index patients; 271 child contacts Household screening and IPT initiation/completion assessment 218/271 (80%) evaluated; nine diagnosed with TB; 70/209 eligible contacts initiated IPT; 16 completed treatment. 6 Evaluation of systematic contact investigation (2015) Rajnandgaon, Chhattisgarh Community-based contact investigation 312 index patients; 1,556 household contacts Symptom screening followed by radiography and sputum investigation 148/1,556 (9.5%) contacts were symptomatic; the study evaluated active TB case detection through household investigation. 7 Nair et al. (2016) Chennai, Tamil Nadu Retrospective record-based study 643 contacts identified; 544 screened Symptom screening, chest radiography and further diagnostic assessment Active TB identified in 29/544 (5.3%) screened contacts; number needed to screen was approximately 19. 8 Bhopal childhood IPT implementation study (2017) Bhopal, Madhya Pradesh Mixed-methods study 129 index patients; 59 child contacts identified Child-contact screening, IPT uptake and qualitative assessment of barriers Among 51 contacted children, 19 (37%) were screened; 11/50 (22%) started IPT and 10/50 (20%) completed treatment. 9 Chatla et al. (2018) Andhra Pradesh and Telangana Systematic contact-screening intervention 4,858 contacts identified; 4,771 screened Symptom screening followed by Xpert MTB/RIF testing Among 781 symptomatic contacts tested, 34 (4.4%) had bacteriologically confirmed TB; 15 had rifampicin resistance. 10 Child-contact screening barriers study (2018) Pune, Maharashtra Observational questionnaire and record-based study 80 adult index cases; 178 child contacts Contact screening, healthcare-worker counselling and IPT assessment 49/178 (28%) child contacts screened; 16 diagnosed with TB; 28 eligible screen-negative children prescribed IPT. 11 Urban household-contact screening study (2020) Urban India Programme implementation study 2,150 contacts screened Household-contact cards, registers, symptom screening and periodic follow-up Screening coverage increased from 36% to 80%; 21 contacts initiated TB treatment and 81/138 young children initiated preventive therapy. 12 Chest radiography and Xpert impact study (2020) Chennai, Tamil Nadu Retrospective cohort 5,553 household contacts screened Symptom screening, chest radiography, smear microscopy and Xpert MTB/RIF 1,312 (23.6%) contacts screened positive by symptoms or radiography; 35 bacteriologically positive cases identified. 13 MDR-TB household-contact study (2021) Agra, Uttar Pradesh Prospective observational study 271 symptomatic contacts of 87 index cases Active TB evaluation and drug-resistance assessment Active TB reported in 97/271 (35.8%); 62 MDR-TB and 35 drug-susceptible cases. 14 South Indian TB infection cohort (2021) South India Cohort study 1,523 household contacts TB infection testing and assessment of exposure-related factors TB infection prevalence of 52.6% (95% CI: 50.1–55.1%); age and bed-sharing associated with infection. 15 Samudyatha et al. (2023) Kolar, Karnataka Explanatory mixed-methods study 301 index patients; 838 household contacts Contact screening, IGRA assessment and TPT follow-up 765/838 (91.3%) screened; 81/83 advised contacts initiated TPT; 63/81 (77.8%) completed. 16 Sharma et al. (2023) Delhi Prospective observational study 1,067 household contacts underwent TST TST-guided preventive treatment using 3HP 614 contacts accepted TPT; 564 (91.8%) completed 3HP; TST positivity was 61.5%. 17 Pediatric household-contact screening study (2023) Two districts of Karnataka Prospective cohort 686 pediatric household contacts Repeated symptom screening, TST and chest radiography Active TB detected in 2.91% of contacts; repeated screening identified disease missed by symptom assessment alone. 18 Mahajan et al. (2023/2024) Maharashtra Mixed-methods implementation study 4,181 index patients; 14,172 household contacts screened IGRA-based Test and Treat model, radiography and TPT 36 active TB cases detected; 2,159/2,353 eligible contacts initiated TPT; 1,958/2,159 completed. 19 Delhi TPT situation analysis (2024) Three districts, Delhi Mixed-methods implementation evaluation District-level programme data and qualitative participants Contact investigation, TPT programme-readiness assessment and implementation evaluation Reported barriers involving drug availability, staffing, training, longer regimens, counselling and private-sector engagement. 20 Chennai private-sector timeliness study (2024) Chennai, Tamil Nadu Explanatory mixed-methods study 263 index patients; 556 household contacts Seven-day contact listing, one-day screening assessment and seven-day treatment decision (7-1-7) 90% of index patients had contacts listed within seven days; 48% had contact outcomes assessed within one day; 57% met the final seven-day treatment-decision target. 21 Revadi et al. (2025) Bhopal, Madhya Pradesh Longitudinal feasibility study 64 household contacts screened IGRA testing and preventive-treatment cascade monitoring IGRA positivity 74.5%; TPT coverage 55.7%; treatment completion 72.4%. 22 Mukherjee et al. (2025) Murshidabad, West Bengal Community-based cross-sectional study 301 TPT-eligible contacts Contact tracing, symptom screening, TPT initiation and completion assessment 225/301 (74.8%) initiated TPT; 156/225 (69.3%) completed, representing 51.8% of all eligible contacts. 23 Malik et al. (2025) Chhattisgarh Operational programme-data study 4,221 index cases; 11,670 contacts screened Routine contact investigation and linkage to TB care Contact investigation completed for approximately 75% of index cases; 109 contacts diagnosed with active TB. 24 JEET 3HP implementation study (2025) Selected Indian districts Descriptive implementation cohort Programme cohort of household contacts receiving TPT Short-course isoniazid–rifapentine regimen (3HP) Evaluated programme-level initiation, adverse events and completion of short-course preventive treatment. 25 Kumar et al. (2025) Rural Delhi Community-based cross-sectional study 430 household contacts Contact screening, TPT awareness, initiation and adherence assessment 202/430 (46.9%) screened for active TB; 188/220 aware contacts started TPT; 125/188 (66.5%) completed. 26 Mundra et al. (2026) Maharashtra Retrospective programme-data analysis 133,167 index patients; 406,291 household contacts identified Symptom screening, diagnostic evaluation and TPT care-cascade assessment 386,224 (95.1%) symptom-screened; 101,325/185,502 eligible contacts initiated TPT; 41,480 recorded treatment completion, with 57,191 outcomes missing. 3.3. Household-Contact Screening Coverage and Active TB Detection Screening coverage and diagnostic yield varied considerably across the 26 studies, reflecting differences in household-contact identification, screening algorithms, diagnostic availability, index-patient characteristics, and follow-up practices. Earlier investigations frequently focused on childhood contacts and isoniazid preventive therapy, whereas later studies increasingly incorporated chest radiography, rapid molecular diagnostics, and systematic preventive-treatment care-cascade monitoring. An early Chennai–Vellore programme evaluation reported that only 31 of 220 child contacts (14.1%) underwent TB screening. In Krishna district, Andhra Pradesh, 116 of 172 eligible young child contacts (67.4%) were evaluated. A subsequent South Indian pilot intervention reported successful tracing of 71 of 87 child contacts (81.6%), demonstrating variation in implementation of routine household-contact services. In the prospective Delhi cohort conducted by Singh et al., 83 of 1,206 household contacts providing sputum (6.9%) were culture-positive for Mycobacterium tuberculosis. These included 52 co-prevalent and 31 incident TB cases identified during longitudinal follow-up. Nair et al. reported that 544 of 643 household contacts (84.6%) underwent screening in Chennai. Abnormal chest radiographs were identified in 71 screened contacts (13.1%), while active TB was diagnosed in 29 (5.3%), corresponding to approximately 19 contacts screened per detected case. In Andhra Pradesh and Telangana, Chatla et al. screened 4,771 contacts exposed to drug-resistant TB. Among 781 symptomatic contacts evaluated using Xpert MTB/RIF, 34 (4.4%) had bacteriologically confirmed TB, including 15 with rifampicin resistance. A Chennai study incorporating symptom assessment and radiography screened 5,553 contacts, of whom 1,312 (23.6%) screened positive by symptoms or radiographic findings. Bacteriologically confirmed TB was identified in 35 contacts. An investigation among 271 symptomatic contacts of patients with multidrug-resistant TB in Agra reported 97 active TB diagnoses (35.8%), including 62 MDR-TB cases. This high diagnostic yield reflects a selected symptomatic, high-risk population rather than the overall prevalence among unselected household contacts. More recent investigations demonstrated improved initial screening coverage in several programme settings. Samudyatha et al. reported screening of 765 of 838 identified contacts (91.3%) in rural Karnataka. Mahajan et al. documented 14,172 screened contacts and 36 active TB cases in Maharashtra. In a private-sector contact-investigation study from Chennai, 90% of index patients had contacts listed within seven days, but subsequent screening and treatment-decision milestones were less consistently achieved. The January 2026 Maharashtra programme analysis by Mundra et al. documented symptom screening among 386,224 of 406,291 identified household contacts (95.1%). Of 7,632 symptomatic contacts, 6,348 (83.2%) underwent diagnostic evaluation, and 799 (12.6% of those evaluated) were diagnosed with active TB. The principal screening outcomes are summarized in Table 3. Table 3. Household-contact screening coverage and active tuberculosis detection in selected primary studies Study (year) Study setting Household contacts evaluated Screening/diagnostic strategy Active TB cases detected (n) Detection yield (%) Singh et al. (2013) South Delhi 1,206 contacts providing sputum Sputum culture and longitudinal follow-up 83 6.9 Khaparde et al. (2015) Chhattisgarh 1,556 household contacts Symptom screening, chest radiography and sputum examination 27 total (17 detected through contact investigation) 1.74% total; 1.09% through contact investigation Nair et al. (2016) Chennai, Tamil Nadu 544 screened contacts Symptom assessment, chest radiography and bacteriological investigation 29 5.3 Chatla et al. (2018) Andhra Pradesh and Telangana 781 symptomatic contacts tested Xpert MTB/RIF 34 4.4 Ananthakrishnan et al. (2020) Chennai, Tamil Nadu 5,553 symptom-screened contacts Symptom assessment, chest radiography and microbiological testing 35 bacteriologically positive 0.63 Shadrach et al. (2021) Agra, Uttar Pradesh 271 symptomatic contacts Clinical assessment and drug-resistance investigation 97 35.8 Chawla et al. (2023) Karnataka 686 pediatric contacts Repeated symptom screening, TST and chest radiography 20 2.91 Mahajan et al. (2024) Maharashtra 14,172 screened contacts Contact screening, radiography and diagnostic evaluation 36 0.25 Malik et al. (2025) Chhattisgarh 11,670 screened contacts Programme-based household-contact investigation 109 0.93 Mundra et al. (2026) Maharashtra 6,348 symptomatic contacts completing evaluation Programme-based diagnostic assessment 799 12.6 Table 3. Household-contact screening coverage, diagnostic strategies, and active tuberculosis detection among selected primary studies conducted in India. Detection yields are presented using the original study-specific denominators. Estimates derived from symptomatic contacts, all screened household contacts, and longitudinal cohorts are not directly comparable. 3.4. Tuberculosis Infection Among Household Contacts The assessment of tuberculosis infection varied between studies, with tuberculin skin testing (TST) and interferon-gamma release assays (IGRA) representing the principal diagnostic approaches. A South Indian cohort involving 1,523 household contacts reported a tuberculosis infection prevalence of 52.6% (95% CI: 50.1–55.1%). Increasing age and greater exposure intensity, including bed-sharing, were identified as associated factors. In a Delhi implementation study, 1,067 household contacts underwent TST, with a reported positivity rate of 61.5%. This demonstrated a substantial burden of immunological evidence of infection among the evaluated contacts. In the Maharashtra Test and Treat programme, 10,777 of 14,133 contacts eligible for TB infection evaluation (76.3%) underwent IGRA testing, of whom 2,468 (22.9%) tested positive. Revadi et al. reported IGRA positivity of 74.5% in a Bhopal feasibility study involving 64 household contacts. Variation in these estimates may reflect differences in exposure intensity, age distribution, study selection, testing eligibility, and diagnostic characteristics. Since TST and IGRA are not interchangeable measures of infection prevalence, the findings were summarized descriptively. 3.5. Tuberculosis Preventive Treatment Initiation and Completion TPT initiation and completion were reported across studies examining childhood IPT, shorter preventive-treatment regimens, and expanded programme implementation. Early studies demonstrated substantial gaps in preventive-treatment coverage among children. The Chennai–Vellore evaluation reported IPT initiation in 16 of 84 young child contacts (19.0%). A Krishna district investigation reported IPT initiation in 97 of 116 evaluated children (83.6%). In a South Indian pilot intervention, 53 child contacts initiated IPT, and 39 completed the prescribed regimen. A Tamil Nadu household-based study involving 271 child contacts reported that 70 of 209 eligible contacts initiated IPT, while 16 completed treatment. Among later studies, Samudyatha et al. reported TPT initiation in 81 of 83 advised contacts (97.6%), with completion in 63 of 81 initiators (77.8%). In Delhi, a 3HP implementation study reported treatment acceptance among 614 contacts, of whom 564 completed treatment (91.9% of those accepting treatment). The Maharashtra Test and Treat study reported that 2,159 of 2,353 eligible contacts (91.7%) initiated preventive treatment, and 1,958 of 2,159 initiators (90.6%) completed treatment. In West Bengal, Mukherjee et al. reported treatment initiation among 225 of 301 eligible contacts (74.8%). Of the 225 initiators, 156 (69.3%) completed treatment, representing full-course coverage of 51.8% among all eligible contacts. Revadi et al. reported overall TPT coverage of 55.7% and completion of 72.4% in their Bhopal feasibility study. The January 2026 Maharashtra programme analysis documented treatment initiation among 101,325 of 185,502 eligible contacts (54.6%). Completion was recorded for 41,480 initiators (40.9%), while treatment outcomes were unavailable for 57,191 (56.5%). The principal treatment outcomes are presented in Table 4. Table 4. Tuberculosis preventive treatment initiation and completion among household contacts Study Eligible or treatment-accepting contacts TPT/IPT initiated Completed Completion outcome Chennai–Vellore (2009) 84 young children 16 (19.0%) Not separately established Initiation reported Krishna district (2011) 116 evaluated children 97 (83.6%) Not separately established Initiation reported Rekha et al. (2013) 87 child contacts identified 53 39 73.6% of initiators Tamil Nadu IPT study (2014) 209 eligible children 70 (33.5%) 16 22.9% of initiators Samudyatha et al. (2023) 83 advised 81 (97.6%) 63 77.8% of initiators Delhi 3HP study (2023) 614 accepted treatment Initiation count not separately established 564 91.9% of those accepting Mahajan et al. (2023/2024) 2,353 eligible 2,159 (91.7%) 1,958 90.6% of initiators Revadi et al. (2025) Reported programme cohort Coverage 55.7% Reported completion 72.4% Source-reported proportion Mukherjee et al. (2025) 301 eligible 225 (74.8%) 156 69.3% of initiators Mundra et al. (2026) 185,502 eligible 101,325 (54.6%) 41,480 documented 40.9% documented completion TPT, tuberculosis preventive treatment; IPT, isoniazid preventive therapy; 3HP, three months of once-weekly isoniazid and rifapentine. Treatment acceptance, treatment initiation, and treatment completion represent different outcomes and are distinguished where the available data permit. The results demonstrated substantial variation in treatment initiation and completion across the identified studies, with differences in eligibility assessment, preventive-treatment regimens, population characteristics, and programme implementation. 3.6. Preventive Treatment Care-Cascade Attrition Losses across the household-contact management cascade were identified in both childhood IPT programmes and more recent large-scale TPT implementation studies. Earlier investigations documented incomplete screening and preventive-treatment initiation among eligible child contacts. In the Chennai–Vellore evaluation, only 31 of 220 children underwent screening, while 16 of 84 children younger than six years initiated IPT. In the Maharashtra Test and Treat study, attrition was observed between initial screening, IGRA testing, eligibility assessment, and treatment initiation. Of 14,133 contacts eligible for TB infection evaluation, 10,777 underwent IGRA testing, and 2,159 of 2,353 contacts subsequently eligible for TPT initiated treatment. The January 2026 Maharashtra programme analysis provided detailed information on the entire care cascade. Among 406,291 contacts identified, 386,224 underwent symptom screening. Of 185,502 contacts recorded as eligible for TPT, 101,325 initiated treatment. Among treatment initiators, 41,480 had documented completion, 2,654 had documented non-completion, and 57,191 had no recorded treatment outcome. The principal care-cascade indicators are presented in Table 5. Table 5. Household-contact screening and preventive-treatment care cascade in Maharashtra (Mundra et al., 2026) Care-cascade indicator Number Percentage Pulmonary TB index patients evaluated 133,167 100% Index patients with contact tracing 112,034 84.1% Household contacts identified 406,291 — Household contacts symptom-screened 386,224 95.1% of identified Symptomatic contacts 7,632 2.0% of screened Symptomatic contacts evaluated 6,348 83.2% of symptomatic Active TB diagnosed 799 12.6% of evaluated Diagnosed contacts initiated on TB treatment 649 81.2% of diagnosed Contacts recorded as TPT-eligible 185,502 45.7% of identified Eligible contacts initiating TPT 101,325 54.6% of eligible TPT completion documented 41,480 40.9% of initiators TPT non-completion documented 2,654 2.6% of initiators Treatment outcome not recorded 57,191 56.5% of initiators TB, tuberculosis; TPT, tuberculosis preventive treatment. Percentages were calculated using the corresponding denominator at each stage of the programme. The findings demonstrate substantial differences between initial screening coverage and subsequent preventive-treatment uptake. In addition, incomplete treatment-outcome documentation affected the interpretation of final programme performance. 3.7. Timeliness of Household-Contact Screening and TPT Initiation Timeliness of household-contact evaluation was assessed in studies examining delays between index-patient diagnosis, contact identification, screening, diagnostic testing, and preventive-treatment initiation. In the Maharashtra Test and Treat programme, the median interval between initiation of treatment for the index patient and household-contact screening was 31 days (IQR: 14–93 days). The median interval from screening to IGRA testing was 16 days, while the median interval from index-patient treatment initiation to TPT initiation was 64 days. A Chennai private-sector study evaluating a 7-1-7 contact-management approach reported that 90% of index patients had contacts listed within seven days. However, 48% had contact outcomes assessed within the subsequent one-day target, and 57% met the final seven-day treatment-decision target, indicating variable achievement of the programme milestones. The reported intervals from the Maharashtra implementation study are summarized in Table 6. Table 6. Timeliness of screening and preventive-treatment delivery in the Maharashtra Test and Treat programme Care-cascade interval Median days Interquartile range Index-patient treatment initiation to contact screening 31 14–93 Contact screening to IGRA testing 16 3–53 IGRA testing to TPT initiation 12 7–23 Contact screening to TPT initiation 31 14–68 Index-patient treatment initiation to TPT initiation 64 35–107.8 TPT initiation to completion 183 180–191 IGRA, interferon-gamma release assay; TPT, tuberculosis preventive treatment; IQR, interquartile range. These observations indicate that programme delays occurred at several stages of household-contact investigation, particularly between index-patient treatment initiation and preventive-treatment commencement. 3.8. Factors Associated With TPT Coverage Several studies evaluated demographic, clinical, and health-system factors associated with tuberculosis infection, screening completion, and preventive-treatment uptake. In the South Indian TB infection cohort, increasing age and closer household exposure, including bed-sharing, were associated with a higher likelihood of infection. Mukherjee et al. evaluated factors associated with TPT coverage among household contacts in West Bengal. Multivariable logistic regression identified significant associations between TPT coverage and male sex, individual household tracing and counselling, and completion of symptom screening. The reported adjusted effect estimates are presented in Table 7. Table 7. Factors associated with tuberculosis preventive-treatment coverage among household contacts in West Bengal Associated factor Adjusted odds ratio (aOR) 95% confidence interval Male sex 1.982 1.004–3.915 Individual household tracing and counselling 13.507 6.781–26.906 Completion of symptom screening 5.694 2.223–14.587 Effect estimates were reported by Mukherjee et al. (2025) and represent associations observed within that study population rather than pooled effects. The strongest association was observed for individual household tracing and counselling, suggesting that direct engagement with household contacts may be an important correlate of treatment coverage. Other studies emphasized the roles of diagnostic accessibility, programme organization, counselling, and treatment follow-up in facilitating successful progression through the care cascade. 3.9. Barriers to Screening and Preventive Treatment Operational barriers were identified across multiple stages of household-contact identification, disease screening, preventive-treatment initiation, and treatment completion. Earlier childhood-contact investigations reported incomplete contact enumeration, limited screening coverage, and difficulties implementing IPT through routine programme services. Subsequent implementation studies identified delayed household visits, incomplete diagnostic evaluation, insufficient counselling, limited access to infection testing, and fragmented referral pathways. In West Bengal, failure of healthcare personnel to offer preventive treatment accounted for 59.2% of reported reasons for non-initiation. Among individuals who did not adhere to treatment, perceived lack of need for TPT and migration accounted for 50.7% and 21.7% of reported reasons, respectively. The Delhi programme situation analysis identified challenges involving staffing, training, drug availability, longer preventive-treatment regimens, counselling, and private-sector engagement. Large-scale programme-data investigations additionally demonstrated incomplete treatment-outcome documentation and losses during follow-up. The principal implementation barriers are summarized in Table 8. Table 8. Major barriers to household-contact screening and preventive-treatment implementation Domain Reported barrier Potential consequence Contact identification Incomplete household enumeration Eligible contacts not reached Household visits Unavailability of contacts during scheduled visits Delayed or incomplete screening Diagnostic evaluation Restricted access to radiography, IGRA or microbiological testing Incomplete disease evaluation Counselling Limited awareness of preventive-treatment benefits Reduced treatment acceptance TPT initiation Eligible contacts not offered treatment Lower treatment initiation Treatment adherence Perceived lack of treatment necessity Treatment interruption Patient mobility Migration during preventive therapy Loss to follow-up Healthcare delivery Staffing, training and coordination constraints Delayed care-cascade progression Programme monitoring Incomplete treatment-outcome documentation Uncertainty in reported treatment completion Public–private coordination Incomplete integration of private providers Delayed contact identification and referral The findings indicate that implementation challenges extend beyond diagnostic screening and involve the entire contact-management pathway. 3.10. Risk of Bias Assessment The methodological characteristics of the 26 primary studies were examined with attention to participant selection, ascertainment of tuberculosis screening and preventive-treatment outcomes, confounding, and completeness of follow-up. The studies represented different observational, interventional, mixed-methods, and programme-based designs, necessitating the use of design-specific methodological assessment frameworks. The principal concerns varied according to study design. Retrospective and programme-data investigations were particularly vulnerable to incomplete contact enumeration, missing diagnostic information, and inconsistent recording of treatment outcomes. Cross-sectional studies were affected by potential selection bias and limited control of confounding, while prospective investigations required consideration of follow-up completeness and consistency of outcome assessment. Studies involving symptom-selected household contacts were susceptible to differential diagnostic verification because individuals without symptoms did not always undergo equivalent microbiological evaluation. In preventive-treatment studies, differences in eligibility criteria, treatment initiation definitions, and outcome ascertainment complicated comparisons between programmes. Missing outcome information was particularly prominent in the large Maharashtra programme analysis by Mundra et al., where final preventive-treatment outcomes were unavailable for 56.5% of initiators. This limited the reliability of the documented treatment-completion proportion as an estimate of actual programme-level completion. The study-specific methodological concerns are summarized in Table 9. Overall, limitations relating to participant selection, incomplete diagnostic verification, variable outcome definitions, and missing follow-up information were important considerations when interpreting the synthesized findings. Table 9. Study-Level Methodological Assessment and Potential Sources of Bias Among the Included Primary Studies. No. Study (year) Appraisal framework Potential selection bias Outcome measurement concerns Missing data / follow-up concerns 1 Rekha Banu et al. (2009) JBI cross-sectional Incomplete inclusion of eligible child contacts Reliance on programme documentation Incomplete screening and IPT follow-up 2 Pothukuchi et al. (2011) JBI cross-sectional Selection of contacts successfully reached Programme-record-based screening ascertainment Incomplete evaluation of eligible children 3 Rekha et al. (2013) JBI cohort / intervention appraisal Small pilot population Programme-related outcome ascertainment Incomplete treatment follow-up 4 Singh et al. (2013) JBI cohort Variation in availability of sputum specimens Culture-based case ascertainment Potential incomplete longitudinal follow-up 5 Shivaramakrishna et al. (2014) JBI cross-sectional Incomplete evaluation of child contacts Reliance on IPT programme records Incomplete treatment completion data 6 Khaparde et al. (2015) JBI prevalence Differential participation in screening Diagnostic evaluation dependent on screening pathway Incomplete diagnostic follow-up 7 Nair et al. (2016) JBI prevalence Contacts not undergoing screening Retrospective diagnostic ascertainment Missing routine screening records 8 Singh AR et al. (2017) MMAT Small child-contact sample Programme-record and interview-based assessment Incomplete IPT follow-up 9 Chatla et al. (2018) JBI prevalence / intervention appraisal Evaluation concentrated among symptomatic contacts Differential microbiological verification Potential undetected disease among screen-negative contacts 10 Belgaumkar et al. (2018) JBI cross-sectional Recruitment restricted to selected index patients Questionnaire and record-based outcomes Incomplete contact-screening information 11 Velayutham et al. (2020) JBI cohort / intervention appraisal Possible differences in programme populations Changes in screening procedures over time Variable follow-up completeness 12 Ananthakrishnan et al. (2020) JBI cohort Selection of contacts completing evaluation Differences in diagnostic testing Incomplete bacteriological verification 13 Shadrach et al. (2021) JBI cross-sectional Symptomatic contacts only Drug-resistance and active-TB assessment Limited generalizability to all contacts 14 Krishnamoorthy et al. (2021) JBI cohort Selection of participating households TB infection testing and exposure classification Potential missing exposure information 15 Samudyatha et al. (2023) MMAT Selection of contacts entering the TPT cascade Mixed programme and interview data Incomplete treatment outcomes 16 Sharma et al. (2023) JBI cohort Selection of TST-tested and treatment-accepting contacts Treatment acceptance versus confirmed initiation Possible incomplete treatment follow-up 17 Chawla et al. (2023) JBI cohort Selection of pediatric contacts Repeated screening and diagnostic verification Follow-up completeness 18 Mahajan et al. (2024) MMAT Attrition before IGRA testing Different denominators across the TPT cascade Incomplete eligibility and outcome ascertainment 19 Alvi et al. (2024) MMAT Selection of programme districts and interviewees Integration of quantitative and qualitative findings Incomplete programme records 20 Thekkur et al. (2024) MMAT Private-sector sample representativeness Measurement of timeliness milestones Incomplete milestone and outcome recording 21 Revadi et al. (2025) JBI cohort Small feasibility-study population IGRA and TPT outcome ascertainment Potential loss to follow-up 22 Mukherjee et al. (2025) JBI analytical cross-sectional Selection of eligible contacts Treatment uptake and adherence measurement Missing-data and confounding considerations 23 Malik et al. (2025) JBI prevalence Incomplete programme contact enumeration Routine programme-data quality Missing screening and diagnostic outcomes 24 Das et al. (2025) JBI cohort Selection of programme treatment recipients Treatment completion and adverse-event documentation Incomplete outcome ascertainment 25 Kumar et al. (2025) JBI analytical cross-sectional Community sample selection Self-reported awareness and treatment outcomes Potential recall and nonresponse bias 26 Mundra et al. (2026) JBI cohort / descriptive appraisal Incomplete contact eligibility ascertainment Routine programme outcome recording Extensive missing TPT outcomes (56.5%) 3.11. Quantitative Synthesis and Heterogeneity Considerable clinical and methodological heterogeneity was observed across the 26 identified studies. Study populations included young children, general household-contact populations, symptomatic contacts, and individuals exposed to drug-resistant tuberculosis. Screening strategies differed in their use of symptom assessment, chest radiography, sputum culture, molecular diagnostics, TST, and IGRA. Active TB detection estimates were calculated using different denominators, including all household contacts, screened contacts, symptomatic contacts, and microbiologically evaluated contacts. Preventive-treatment initiation and completion were similarly reported among contacts advised treatment, contacts classified as eligible, treatment recipients, or contacts with documented treatment outcomes. Differences in programme setting, treatment regimens, observation periods, and data completeness further contributed to heterogeneity. Given these differences, a narrative synthesis was undertaken. No pooled meta-analysis was performed, and pooled effect estimates, I² statistics, and publication-bias analyses were therefore not calculated. 3.12. Overall Summary of Findings The evidence synthesized from the 26 study entries demonstrated variation in household-contact screening coverage, active tuberculosis detection, TB infection prevalence, and preventive-treatment implementation across Indian settings. Earlier studies frequently identified gaps in childhood contact screening and isoniazid preventive therapy, whereas more recent implementation studies reported greater screening coverage but persistent attrition during eligibility assessment, treatment initiation, and follow-up. Active TB detection yields differed substantially between general household-contact investigations and studies restricted to symptomatic or drug-resistant TB exposure populations. Tuberculosis infection was frequently identified among evaluated contacts, although prevalence estimates varied according to population characteristics and diagnostic approach. TPT initiation and completion also varied across programmes. Studies with strong treatment linkage reported relatively high completion among initiators, while large routine programme evaluations revealed incomplete preventive-treatment coverage and substantial missing outcome documentation. Household tracing, counselling, diagnostic accessibility, and timely follow-up emerged as important components of the contact-management pathway. Overall, the findings demonstrate the importance of evaluating the complete household-contact care cascade, from contact identification and active TB screening to preventive-treatment initiation, completion, and documentation of outcomes.

4.1. Principal Findings The present systematic review synthesized evidence from 26 primary-study entries investigating tuberculosis (TB) screening strategies, active case detection, tuberculosis infection, and tuberculosis preventive treatment (TPT) implementation among household contacts in India. The findings demonstrate substantial variation in screening coverage, diagnostic yield, preventive-treatment initiation, and treatment completion across geographical regions, healthcare settings, and study populations. Although household-contact investigation represents an important opportunity for early detection and prevention of TB, the evidence highlights persistent challenges in translating screening activities into comprehensive preventive care. A major finding was the considerable variation in active TB detection across the identified studies. Detection yields ranged from approximately 0.25% in a large Maharashtra implementation study to 35.8% among symptomatic household contacts of patients with multidrug-resistant TB (MDR-TB) in Agra. These estimates were derived from fundamentally different populations and diagnostic pathways and therefore should not be interpreted as direct comparisons of screening effectiveness. Studies restricted to symptomatic or high-risk contacts generally reported higher diagnostic yields than investigations involving broader household-contact populations. Preventive-treatment outcomes were similarly heterogeneous. TPT initiation among eligible or advised contacts ranged from 54.6% in the large Maharashtra programme analysis to 97.6% in a Karnataka implementation study. Completion among treatment initiators also varied considerably. Importantly, large programme evaluations demonstrated that high initial screening coverage did not necessarily translate into comparable preventive-treatment uptake or documented completion. Together, these findings emphasize the importance of assessing the complete household-contact management pathway, rather than relying exclusively on screening coverage or treatment initiation as indicators of programme success. 4.2. Importance of Household-Contact Investigation for Early Tuberculosis Detection Household-contact investigation remains an essential component of tuberculosis prevention because individuals living with patients with infectious pulmonary TB are exposed to repeated opportunities for transmission. Prolonged exposure within shared living environments, particularly where overcrowding and inadequate ventilation are present, may increase the likelihood of infection and subsequent progression to active disease. The findings of the present review support the value of systematic household-contact investigation for identifying previously undiagnosed active TB. In the prospective Delhi cohort by Singh et al., 83 of 1,206 sputum-providing contacts were culture-positive, including 52 co-prevalent and 31 incident cases. This observation indicates that contact investigation may identify both disease already present at the time of the initial assessment and disease developing during subsequent follow-up. Similarly, Nair et al. reported active TB in 5.3% of screened contacts in Chennai, corresponding to approximately one detected case for every 19 contacts screened. These findings illustrate the potential diagnostic value of systematic contact investigation in high-burden settings. However, the magnitude of screening yield differed substantially between studies. The lower proportion of active TB detected in the Maharashtra Test and Treat programme compared with the Chennai investigation may reflect differences in background epidemiology, contact selection, screening procedures, diagnostic confirmation, and the timing of evaluation. The particularly high proportion of active TB observed among symptomatic contacts of MDR-TB patients in Agra should be interpreted within the context of its selected, high-risk population. Such findings should not be generalized to all household contacts of individuals with drug-susceptible pulmonary TB. These observations reinforce the need for screening strategies adapted to exposure risk, index-patient characteristics, and the diagnostic resources available within the healthcare system. 4.3. Comparative Implications of Household-Contact Screening Strategies The studies included in this review employed several screening approaches, ranging from symptom-based assessment to integrated strategies incorporating chest radiography, sputum microscopy, mycobacterial culture, and rapid molecular diagnostic testing. Symptom-based screening was frequently used as the initial contact-evaluation strategy because it is relatively inexpensive, operationally straightforward, and feasible for implementation through frontline healthcare workers. This approach is particularly relevant in resource-constrained community settings where advanced diagnostic facilities may not be readily accessible. However, reliance on symptoms alone may result in missed opportunities to detect asymptomatic or subclinical pulmonary TB. Studies incorporating chest radiography demonstrated that radiological assessment can identify individuals requiring further diagnostic evaluation, including those without prominent respiratory symptoms. The Chennai radiography/Xpert study reported that 1,312 of 5,553 contacts screened positive through symptom assessment or radiographic evaluation, highlighting the potential contribution of combined screening approaches to identifying presumptive TB. Rapid molecular diagnostic tests provide additional value by facilitating microbiological confirmation and detection of rifampicin resistance. In the Andhra Pradesh and Telangana investigation, 15 of 34 bacteriologically confirmed cases identified among symptomatic contacts had rifampicin resistance. This finding highlights the importance of timely drug-resistance evaluation among contacts exposed to patients with drug-resistant TB. The findings are consistent with WHO recommendations supporting systematic TB screening among household contacts and the use of appropriate diagnostic investigations to identify active disease. Screening strategies should incorporate the availability of molecular diagnostics, radiography, and clinical evaluation while considering the characteristics of the population being screened. Nevertheless, direct evidence comparing the effectiveness of individual screening algorithms was limited. Consequently, the present findings support the practical value of integrated screening but do not establish the superiority of one diagnostic algorithm across all Indian settings. 4.4. Tuberculosis Infection Burden and Implications for Preventive Treatment The substantial burden of tuberculosis infection reported among household contacts further emphasizes the importance of preventive interventions. The South Indian cohort involving 1,523 contacts reported an infection prevalence of 52.6%, while the Delhi 3HP implementation study documented TST positivity of 61.5%. In contrast, the Maharashtra Test and Treat programme reported IGRA positivity of 22.9% among those tested, and the Bhopal feasibility study reported a substantially higher positivity proportion of 74.5%. These differences may reflect heterogeneity in exposure intensity, age distributions, background epidemiology, eligibility for infection testing, and diagnostic procedures. Because TST and IGRA assess immunological responses to TB antigens rather than directly identifying viable bacilli or distinguishing active from latent infection, their results require interpretation within the clinical and epidemiological context. The observed associations between infection and age or close household exposure also suggest that infection risk is not distributed uniformly within households. Importantly, TB infection testing is not required for every eligible contact before preventive treatment. WHO and Indian programme guidance support preventive treatment for specified high-risk groups after active TB has been appropriately excluded, including young child household contacts for whom routine infection testing may not be feasible or necessary. The findings therefore support a risk-based and guideline-consistent approach to TPT eligibility assessment, rather than universal dependence on TB infection testing as a prerequisite for preventive treatment. 4.5. Evolution of Tuberculosis Preventive Treatment Implementation in India The studies reviewed demonstrate an evolution in household-contact preventive care in India, from predominantly childhood-focused isoniazid preventive therapy (IPT) to broader tuberculosis preventive treatment strategies addressing eligible household contacts across different age groups. Earlier investigations, including the Chennai–Vellore programme evaluation and studies from Andhra Pradesh, Tamil Nadu, and Madhya Pradesh, identified important gaps in childhood-contact investigation and IPT delivery. Although young child household contacts represented a priority population for preventive therapy, screening and treatment initiation were frequently incomplete. These findings suggest that limited preventive-treatment coverage was not solely attributable to clinical eligibility but was also influenced by challenges in contact identification, healthcare-worker engagement, counselling, and follow-up. More recent studies demonstrated improvements in the operational delivery of preventive treatment. Samudyatha et al. reported TPT initiation among 97.6% of advised contacts, while the Maharashtra Test and Treat programme achieved initiation among 91.7% of eligible individuals. These findings indicate that high treatment uptake is achievable when contacts successfully progress through screening and eligibility assessment. However, larger programme-level evaluations revealed substantial differences between treatment uptake within selected eligible groups and coverage across the wider household-contact population. The January 2026 Maharashtra analysis documented TPT initiation in 54.6% of eligible contacts despite symptom-screening coverage exceeding 95%. This difference suggests that programme performance should be evaluated across the complete care cascade rather than using screening coverage alone. The findings align with India's programmatic approach to TPT, which emphasizes household-contact identification, active disease exclusion, treatment eligibility, adherence support, and systematic outcome monitoring. 4.6. Preventive Treatment Completion and the Potential Role of Shorter Regimens Preventive-treatment completion represents a critical implementation outcome because treatment initiation does not necessarily translate into receipt of the prescribed preventive regimen. The reviewed studies demonstrated considerable variation in treatment completion, ranging from relatively low completion in some early childhood IPT programmes to completion exceeding 90% among treatment initiators in selected contemporary implementation cohorts. The Maharashtra Test and Treat study reported treatment completion among 90.6% of initiators, while the rural Karnataka implementation study documented completion among 77.8%. In West Bengal, completion was recorded among 69.3% of treatment initiators, corresponding to full-course coverage of only 51.8% among all eligible contacts. The Delhi 3HP implementation study reported completion in 564 of 614 individuals accepting the regimen, suggesting that shorter preventive-treatment approaches can achieve favourable completion in selected programme settings. Shorter rifamycin-containing preventive-treatment regimens may improve programme acceptability by reducing the duration of treatment and the number of doses required. WHO guidance includes three months of weekly isoniazid and rifapentine (3HP) and three months of daily isoniazid and rifampicin (3HR), among other recommended preventive-treatment options. Nevertheless, the observational nature of the available Indian implementation evidence limits direct comparisons of regimen effectiveness or adherence. Differences in eligibility, counselling, treatment support, participant characteristics, and outcome ascertainment may influence reported completion. An additional concern was the substantial proportion of missing treatment outcomes in large programme datasets. Mundra et al. reported documented completion for 40.9% of TPT initiators, but outcomes were unavailable for 56.5%. Therefore, the documented completion proportion should not be interpreted as the true treatment-completion probability among all recipients. Improving treatment adherence requires both appropriate regimen selection and reliable follow-up systems capable of identifying interrupted treatment, managing adverse effects, and recording final outcomes. 4.7. Attrition Across the Household-Contact Management Cascade A consistent finding across the evidence was that losses occurred at multiple stages of household-contact management. Earlier studies frequently reported inadequate enumeration and screening of child contacts. More recent investigations documented substantial screening coverage but continued losses during diagnostic evaluation, infection testing, preventive-treatment initiation, and treatment follow-up. In the Maharashtra Test and Treat programme, only 76.3% of contacts eligible for TB infection evaluation underwent IGRA testing. Although preventive-treatment initiation and completion were high among contacts who successfully reached those stages, earlier losses reduced overall access to the intervention. The larger Maharashtra programme analysis demonstrated a similar pattern. Despite symptom screening in 95.1% of identified contacts, only 54.6% of those recorded as eligible for TPT initiated treatment. These findings highlight the importance of distinguishing stage-specific performance from cumulative programme coverage. For example, a programme may achieve high treatment completion among individuals who commence TPT but still provide complete preventive treatment to a relatively small proportion of all eligible contacts if substantial losses occur before initiation. The household-contact care cascade therefore provides a comprehensive framework for identifying missed opportunities, defining programme indicators, and monitoring service delivery. Future programme evaluations should consistently report the numbers of contacts identified, screened, evaluated, eligible, initiated on TPT, and completing treatment, together with clearly defined denominators and reasons for attrition. 4.8. Timeliness of Household-Contact Investigation and Preventive Treatment Timeliness emerged as another important dimension of household-contact management. The Maharashtra Test and Treat study reported a median interval of 31 days between index-patient treatment initiation and household-contact screening, while the median interval to TPT initiation was 64 days. These findings demonstrate that identification of an index TB patient does not automatically translate into timely preventive-treatment delivery for household members. Delays may arise from postponed household visits, difficulty locating contacts, diagnostic-service availability, infection-test processing, eligibility evaluation, or fragmented referrals. The Chennai private-sector implementation study showed that performance differed across successive contact-management milestones, despite relatively high early contact-listing coverage. Prompt household-contact investigation is particularly important among young children and other individuals at increased risk of progression to active disease. Integrating contact investigation into routine index-patient notification, using defined timelines for household visits, and facilitating coordinated diagnostic and treatment services may help reduce delays. Digital tracking systems and appropriately trained frontline healthcare workers may further improve timely follow-up and continuity of care. 4.9. Determinants of TPT Uptake and the Importance of Counselling The reviewed studies identified several factors associated with successful progression through preventive-treatment services. In West Bengal, Mukherjee et al. reported a strong association between individual household tracing and counselling and TPT coverage (adjusted odds ratio: 13.507; 95% CI: 6.781–26.906). Completion of symptom screening was also positively associated with coverage. These findings suggest that direct contact with household members and clear communication regarding the benefits of preventive therapy may support treatment acceptance. Qualitative and programme-based investigations identified limited awareness, inadequate counselling, perceived lack of treatment necessity, and failure to offer eligible contacts preventive treatment as important barriers. A particular challenge in preventive therapy is that eligible individuals frequently do not have symptoms of active TB disease. Consequently, the benefits of treatment may not be immediately apparent to patients or their families. Effective counselling should explain the relationship between household exposure, tuberculosis infection, future disease risk, and the purpose of preventive treatment. Counselling should also address expected treatment duration, adverse effects, medication adherence, follow-up requirements, and circumstances requiring clinical evaluation. However, the observational nature of the reported associations means that counselling cannot be regarded as the sole causal determinant of increased treatment uptake. Programme-level interventions should be evaluated prospectively to determine their independent effectiveness. 4.10. Implications for Children and Contacts of Drug-Resistant Tuberculosis Children remain a particularly important population for household-contact investigation because of their vulnerability to progression from infection to active disease, particularly at younger ages. Several early Indian studies documented low childhood-contact screening coverage and incomplete implementation of IPT. These findings demonstrate that eligibility recommendations alone may not ensure access to preventive treatment. Childhood-contact programmes require systematic enumeration, age-appropriate screening, timely exclusion of active disease, and preventive treatment according to current national recommendations. The findings also demonstrate the importance of contact investigation among individuals exposed to drug-resistant TB. The Andhra Pradesh and Telangana screening intervention identified rifampicin resistance in 15 of 34 bacteriologically confirmed TB cases among evaluated symptomatic contacts. This highlights the need for appropriate microbiological investigation and drug-resistance assessment when active disease is suspected. The management of contacts exposed to MDR-TB or rifampicin-resistant TB requires particular attention to the drug-susceptibility profile of the index case and appropriate preventive-treatment regimens. Updated WHO guidelines recommend six months of daily levofloxacin as a preventive-treatment option for eligible contacts exposed to MDR/RR-TB, subject to clinical considerations and programme guidance. These recommendations reinforce the need for individualized assessment rather than applying an identical preventive-treatment strategy to all household contacts. 4.11. Implications for the National Tuberculosis Elimination Programme The findings have important implications for strengthening household-contact screening and preventive-treatment delivery under India's National Tuberculosis Elimination Programme (NTEP). First, contact investigation should be integrated into routine care immediately after diagnosis and notification of the index TB patient. Systematic enumeration of household members and defined responsibilities for follow-up may improve screening coverage. Second, screening strategies should incorporate appropriate clinical assessment, chest radiography, and microbiological testing according to the individual risk profile and national recommendations. Particular attention should be given to children, symptomatic contacts, immunocompromised individuals, and contacts of patients with drug-resistant TB. Third, preventive-treatment services should be organized to minimize delays between screening, eligibility assessment, and treatment initiation. Decentralized diagnostic and treatment services may reduce the need for repeated visits to higher-level facilities. Fourth, adherence support should extend beyond initial counselling to include treatment follow-up, adverse-event monitoring, and timely management of interruptions. Fifth, programme monitoring should use standardized indicators with clearly defined denominators. Contact screening, TPT eligibility, initiation, completion, and missing outcomes should be reported separately. Finally, greater coordination between public healthcare services, private providers, community healthcare workers, and programme monitoring systems may help improve continuity of care. These measures align with WHO guidance emphasizing comprehensive preventive-treatment services across the entire cascade of care. 4.12. Strengths and Limitations A major strength of the present review is its integrated examination of household-contact screening and preventive-treatment implementation in India. By considering both active TB detection and preventive-treatment outcomes, the synthesis provides a broader perspective on household-contact management than studies focusing on individual stages of care. The evidence spans different geographical regions, programme settings, age groups, and diagnostic approaches, allowing important variations in service delivery to be described. Inclusion of earlier childhood IPT studies alongside more recent TPT implementation studies also provides insight into changes in preventive-treatment delivery over time. Nevertheless, several limitations should be considered when interpreting the findings. The included studies demonstrated considerable clinical and methodological heterogeneity, particularly in population selection, contact definitions, screening algorithms, diagnostic confirmation, treatment eligibility, and outcome reporting. Several investigations relied on routinely collected programme data, which may be affected by incomplete contact enumeration, missing diagnostic information, and incomplete follow-up. Some studies evaluated highly selected populations, including symptomatic contacts or contacts of patients with drug-resistant TB, limiting generalizability to broader household-contact populations. The evidence also consisted predominantly of observational and programme-based investigations, restricting causal interpretation of associations between implementation strategies and treatment outcomes. Differences in outcome denominators and the possibility of overlapping programme populations limited the appropriateness of quantitative pooling. Consequently, a narrative synthesis was used rather than meta-analysis. Furthermore, missing treatment outcomes in some large-scale studies introduced uncertainty in estimating true preventive-treatment completion. These limitations should be considered when extrapolating the findings to national programme performance or comparing results across geographical settings. 4.13. Future Research Directions Future research should prioritize prospective, multicentre investigations using standardized definitions for household-contact identification, screening completion, diagnostic yield, preventive-treatment eligibility, initiation, and completion. Comparative studies are needed to evaluate the effectiveness and cost-effectiveness of symptom-based screening, chest radiography, molecular diagnostic testing, and integrated screening algorithms in different epidemiological and resource settings. Additional research should examine methods for improving the identification of asymptomatic and subclinical TB among household contacts. Longitudinal studies are also required to determine the extent to which improved screening and TPT delivery reduce subsequent active TB incidence. The implementation of shorter preventive-treatment regimens should be evaluated with respect to treatment completion, adverse events, patient acceptability, and programme cost. Particular attention should be given to children, adolescents, contacts of patients with drug-resistant TB, migrant populations, and households receiving care through private healthcare providers. Implementation research should also investigate the effectiveness of digital contact-tracing systems, decentralized treatment delivery, structured counselling, and community-health-worker-led follow-up. Standardized reporting of the complete contact-management cascade will be essential for identifying missed opportunities and improving the comparability of future Indian studies. 4.14. Overall Interpretation The findings of this review demonstrate that household-contact investigation offers an important opportunity to strengthen tuberculosis prevention in India by facilitating early disease detection and access to preventive treatment. However, programme success depends on the continuity of care across multiple stages, beginning with contact identification and extending through screening, diagnosis, preventive-treatment eligibility assessment, initiation, and completion. The evidence indicates that improvements in screening coverage have not consistently been accompanied by equivalent improvements in preventive-treatment delivery. Diagnostic delays, incomplete counselling, treatment non-adherence, and missing outcome documentation remain important barriers. Integrated diagnostic strategies, timely household-contact evaluation, accessible preventive treatment, structured counselling, and strengthened programme monitoring may improve the effectiveness of household-contact management. Overall, a coordinated, patient-centred approach that addresses the complete prevention cascade is likely to be more informative for programme strengthening than isolated improvements in individual screening or treatment indicators.

Household-contact screening can detect active tuberculosis in India and create opportunities for preventive treatment. The evidence emphasizes that enumeration and symptom screening must be linked to timely diagnostic assessment, counselling, initiation, completion and reliable outcome documentation. Future prospective comparative and implementation studies should standardize denominators and evaluate clinically meaningful outcomes.

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