Economic development and evolving lifestyle habits significantly influence the public health landscape in developing countries. This shift in health patterns has prompted a reassessment of public health strategies. Every fifth person in India is hypertensive, and more than 80% of patients with chronic kidney disease (CKD) are hypertensive, which contributes to the progression of kidney disease toward the end stage (ESRD) as well as to cardiovascular events such as heart attack and stroke¹. So, close blood pressure monitoring is an essential part of caring for patients withCKD².

There are various options for blood pressure monitoring, home blood pressure monitoring, office (clinic) and twenty-four-hour ABPM (ambulatory blood pressure monitoring). ABPM is superior to clinic BP measurements in diagnosing white-coat hypertension, masked hypertension, predicting end-organ damage and is valuable for detecting nocturnal BP changes, which predict cardiovascular mortality in chronic renal failure disease (CRF)^3,4. Normal ambulatory blood pressure during the day is <135/85 mm Hg and <120/70 mm Hg at night⁵.  Home blood pressure monitoring, which allows for multiple readings over several days, has shown a stronger correlation with organ damage compared to measurements taken in a clinical setting. It seems to be a better prognostic indicator of stroke and cardiovascular mortality and can identify white-coat and masked hypertension. This method could serve as a viable alternative to ambulatory monitoring for diagnosis, especially in primary care environments where resources may be limited or costs prohibitive or when patients find traditional methods inconvenient or uncomfortable^6,7. However, the validity of home BP relative to ABPM and routine office (clinic) BP has not been assessed systemically in patients with CKD, especially in India⁸. So, the present study aimed to detect masked hypertension in CKD patients and investigate whether home BP measurements provide a feasible and reliable alternative to ABPM and repeated office(clinic)BP measurements in differentiating true from white-coat hypertension

Study setting and design: This cross-sectional study was carried out at the tertiary care centre in Uttar Pradesh, India, from March 2016 to July 2017 after the ethical permission of the Institutional Ethical Committee. 

Study population: The study included 75 confirmed cases of CKD presented to OPD in the study setting area.

Inclusion Criteria: Patients having CKD stage 1 to 4 (pre-dialysis) & age more than 18 years.

Exclusion criteria: Patients having accelerated blood pressure, heart disease, dialysis, patients having acute infection, pregnancy, and patients who did not give consent.

Data Collection: In the beginning, the purpose of the study was explained to the subjects in their local language and the investigator obtained written informed consent from eligible candidates who agreed to participate. Patient details were incorporated based on the proforma, including chief complaints, comorbidities, treatment history, general physical and systemic examination, and detailed investigations during the OPD presence. Selected patients were assessed for blood pressure measurement in the clinic, at home, and 24-hour ambulatory blood pressure.

Blood pressure was measured by a standardized semiautomatic oscillometric device (Omron HEM 7120). The device met the criteria for accuracy according to the revised protocol of the British Hypertension Society.

Variables:

Clinic BP measurement: BP was recorded twice at approximately a 2-minute interval by the clinician, with the patient in the sitting position in a quiet room, back supported, arm supported (for example, resting on the table), legs uncrossed, not talking and relaxed, correct cuff bladder placement at heart. Patients requested to refrain from heavy exercise in the morning and to avoid cola drinks, coffee, tea, any drugs and smoking for at least 1 hour before the measurement. BP was measured after the patient rested for 15 minutes. Results were immediately noted down in a specific chart. An average of two second time measurements were concluded.

Home BP measurement: Patients and their attendants were explained and given individual guidance on correctly measuring BP. Preparations for home BP measurement were the same as for clinic BP. Results were immediately noted down in a specific chart. Home BP was determined as the mean of 14-second time measurements.

24-hour ABPM: It was recorded by the standardized auscultatory device (Ambulatory Blood Pressure Monitor) for 1 day with normal routine activities of the patient at home during seven days of home BP measurement. Ambulatory BP was recorded during daytime (6 am to 11 pm) at 30-minute intervals and during nighttime (11 pm to 6 am) at 1-hour intervals. The patient was given individual guidance about ABPM. Systolic BP out of 70 to 250 mm Hg and diastolic BP out of 40 to 150 mm Hg were rejected.

Data entry & analysis: The data were recorded in an Excel sheet, and a descriptive study was performed, of which data are presented in the tables. Chi-square was applied accordingly to determine the association between dependent and independent variables. A p-value less than 0.05 was considered statistically significant.

Table 1 shows that 0.0%, 30.6%, 54.7%, and 14.7% of participants were 18-45, 46-55, 56-65, and 66-75 years respectively and 61.3% participants were male & 38.7% were female. Chronic Kidney Disease (CKD) was noted in 1.3%, 21.3%, 62.7%, and 14.7% participants respectively. Almost 69.3%, 61.3%, and 40% of participants were diagnosed with hypertension by ABPM at home & clinic respectively. 

Table 1: Socio-clinical characteristics of study participants [N=75]

Table 2 shows that the distribution of participants according to the type of HTN and ABPM method of HTN detection was statistically significant (p<0.05). The distribution of participants according to the kind of HTN and home method of HTN detection was statistically significant (p<0.05). The distribution of participants according to the type of HTN detected at the clinic was statistically significant (p<0.05).

Figure 1: Distribution of blood pressure detected by all three methods (ABPP, Home, Clinic) [N=75]

Figure 1 shows that 30.7%, 38.7%, 21.3%, and 1.2% of participants sustained HTN, masked HTN, normotensive & white coat HTN, respectively.

Table 2: Association between type and method of detection of HTN [N=75]

*p-value calculated by Chi-square Test

Table 3 shows that out of all the HTN cases detected by the ABPM method (52), 46 (88.4%) HTN cases were also detected by the home method, and 23 (44.2%) HTN cases were detected at the clinic. Out of all the non-HTN instances detected by the ABPM method (23), 23 (100%) non-HTN cases were also detected by the home method and 16 (69.6%) non-HTN cases were detected at the clinic. The association between the home BP measurement and ABPM methods regarding case detection was statistically significant (p<0.05). The association between clinic BP and ABPM methods regarding case detection was statistically insignificant (p>0.05). 

Table 3: Association between home BP & clinic BP with ABPM measurement method to detect HTN [N=75]

*p-value calculated by Chi-square Test

Out of all the HTN cases detected by the clinic BP method (30), 23 (88.4%) HTN cases were also detected at the home method and out of all the non-HTN instances detected by the clinic BP method (45), 22 (48.9%) non-HTN cases also detected at-home method. The association between the home BP measurement method and the clinic BP method regarding case detection was statistically significant (p<0.05).

Table 4: Association between home BP and clinic BP measurement method to detect HTN [N=75]

*p-value calculated by Chi-square Test

The study observed that sensitivity, specificity, Positive Predictive Value, and Negative Predictive value to detect HTN by the Home BP method compared to the ABPM method was 88.6%, 100%, 100%, and 79.3% and of clinical BP method was 44.2%. 69.6%, 76.7%, 35.6% respectively.

In Our study of 75 patients, ABPM detected almost 2/3 hypertensive patients, the highest among the three methods, compared to 61.33% and 40% for home BP and clinic BP, respectively. Around 38.67% (n-29) of the patients had masked hypertension, whereas only 9.33% (n-7) patients were observed with white coat hypertension, while 30.67% (n-23) and 21.33% (n-16) patients were observed to have sustained hypertension and normotension respectively by correlating three different methods of BP measurements. Pogue V et al.¹ reported that 36.6% of patients had normotension and 21.1% had sustained HTN, which were almost reversed findings in our study. This could be due to a more extensive population study and different parameters and methods to diagnose HTN.

The prevalence of masked hypertension has been reported to be at 10–45%, depending on the definition used and the population studied. In the Ohasama population study (Ohkubo T et al.⁹) in Japan, a 13.4% prevalence has been reported among subjects with normal screening clinic BP. In contrast, in the PAMELA population study (Sega R et al.¹⁰) in Italy, a 9% prevalence was found among untreated subjects. In the SHEAF study (Bobrie G et al.¹¹) in treated elderly hypertensive subjects in France, 11% of participants had masked hypertension. Particularly in CKD patients, Agarwal R et al.¹² reported a prevalence of masked hypertension as 27%. The results of our study were like those of the African American Study of Kidney Disease Cohort study (42.9)⁸, CKD Japan cohort (30.9%)13, APrODiTe study (33.9%)¹⁴, and CRIC Study (27.8%)¹⁵.  

Another general population study of 261 individuals found a similar proportion of masked hypertensive with home and ambulatory BP measurements (10.6 and 11.4%, respectively)⁹. However, diagnostic disagreement between the two methods was common, with only 79.31% of masked hypertensive with ambulatory monitoring having the same diagnosis as home monitoring. A cross-sectional study of 438 subjects done by Stergiou GS et al.¹⁶ attending a BP clinic also found similar proportions of masked hypertensive diagnosed by ambulatory or home BP.

In the present study, clinic BP was higher than home BP or ABPM, whereas no difference existed between home BP and ABPM. In the PAMELA general population study, 70% of those defined as white-coat hypertensives based on ambulatory monitoring had the same diagnosis based on home measurements¹⁰. Another cross-sectional study, which was not allied with our study, reported disagreement between home and ABPM in diagnosing white-coat hypertension in 13% of participants, but it could be due to different methods taken into account. Based on the findings, it has been suggested that home BP is a valuable alternative to ABPM for detecting white coat HTN¹⁷.

In our study population, Home BP achieved a specificity of 100% and a sensitivity of 88.45% for the detection of hypertension when using ABPM as the gold standard. Positive and negative predictive values for home BP were 100% and 79.31%, respectively. The specificity values are comparable to those recently reported for home self-measurements by adult patients, but sensitivity values are higher^17-19. Clinic BP had 44.23% sensitivity and 69.57% specificity. For clinic BP, positive and negative predictive values were 76.67% and 35.56% respectively. The relative mean clinic BP measurement was taken on two different occasions, and home BP had greater sensitivity and specificity.

The limitations of the present study are due to the limited period; the sample size was small, which might have resulted in the statistical insignificance of particular associations that were otherwise expected to be significant, according to the reviewed literature. This was a cross-sectional and observational study; therefore, it has limitations in establishing a cause-effect relationship. Medication timings for treated hypertensive patients were not certain, which could have affected the findings. ABPM was evaluated only once; variability in measurements was not considered. This might result in misclassification. Conditions for home BP measurements for every patient could differ; even timings and instruments were the same, and the material to measure BP at home was explained.

Our study concluded that in CKD patients' clinics, BP was underestimated or overestimated in the detection of hypertension. ABPM was the gold standard for detecting hypertension, especially masked hypertension. Home BP was no longer far behind ABPM in detecting white coat and masked HTN. Home BP measurement provides a better and more feasible option for measuring BP and detecting HTN in CKD. Our study had no follow-up and only one ABPM reading, which might lead to miscalculation. Therefore, large outcome trials with a more extended follow-up period are necessary to confirm or refute the significance of our present findings. It should also be emphasized that our results apply only to the specific population of patients we included in our trial. It would be worthwhile to assess whether home BP measurement has the same implications in patients with comorbid conditions, such as diabetes mellitus, as well as in populations with a different racial background. Finally, the present data may serve as a starting point for more elaborate cost-effectiveness studies and reimbursement of BP monitoring devices.

FUNDING: No funding sources

CONFLICT OF INTEREST: None declared

ETHICAL APPROVAL: The study was approved by the Institutional Ethics Committee

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