Acute appendicitis is one of the most common causes of acute abdomen requiring emergency surgical intervention worldwide. It occurs due to inflammation of the vermiform appendix, usually resulting from luminal obstruction, bacterial overgrowth, and subsequent inflammatory changes.1 Although appendicectomy remains the definitive treatment for confirmed acute appendicitis, accurate preoperative diagnosis continues to be a clinical challenge due to the wide variation in presentation and overlap of symptoms with other causes of right lower quadrant abdominal pain.2,3 The classical presentation of acute appendicitis includes migratory abdominal pain, anorexia, nausea, vomiting, fever, and tenderness in the right iliac fossa. However, atypical presentations are frequent, particularly among elderly patients, children, and females of reproductive age.4 Delayed diagnosis may increase the risk of complications such as perforation, abscess formation, and generalized peritonitis, whereas an incorrect diagnosis may result in unnecessary appendicectomy. Therefore, development of reliable, simple, and cost-effective diagnostic methods is essential for improving clinical decision-making.5 Various diagnostic modalities, including ultrasonography and computed tomography, have improved the evaluation of suspected appendicitis. However, their routine use may be limited by availability, cost, radiation exposure, and dependence on operator expertise.6 Clinical scoring systems provide an alternative approach by combining clinical symptoms, physical examination findings, and laboratory parameters into a standardized diagnostic assessment. These scoring systems assist surgeons in risk stratification and management planning, particularly in resource-limited settings.7 The Alvarado score is one of the most widely used clinical scoring systems for acute appendicitis. It incorporates parameters such as migration of pain, anorexia, nausea and vomiting, tenderness in the right lower quadrant, fever, leukocytosis, and neutrophilia.8 Based on the total score, patients are categorized according to the probability of appendicitis, guiding further evaluation and treatment decisions. Despite its widespread use, variations in diagnostic accuracy have been reported, particularly among different populations.9 The Appendicitis Inflammatory Response (AIR) score was developed to improve diagnostic performance by incorporating inflammatory markers and clinical findings. It includes variables such as vomiting, right lower quadrant pain, rebound tenderness or muscular defense, elevated white blood cell count, proportion of neutrophils, and C-reactive protein levels. The AIR score provides graded risk stratification and may better reflect the severity of inflammatory response associated with acute appendicitis.10,11 Comparison of different scoring systems is important to identify the most reliable tool for preoperative diagnosis. A scoring system with higher diagnostic accuracy can help reduce negative appendicectomy rates, prevent unnecessary delays in surgery, and optimize patient outcomes. From a general surgical perspective, an effective clinical scoring system can support early decision-making, especially where advanced imaging facilities are limited or unavailable. This study provides a direct comparison between two widely used clinical scoring systems, the AIR score and Alvarado score, in diagnosing acute appendicitis within a surgical patient population. AIMS AND OBJECTIVES • To compare the diagnostic accuracy of the Appendicitis Inflammatory Response (AIR) score and Alvarado score in patients with suspected acute appendicitis

A prospective comparative study was conducted in the Department of General Surgery, Sree Mookambika Institute of Medical Sciences, Kulasekharam, Tamil Nadu, over a period of 12 months from January 2025 to December 2025. The study included 56 patients who presented with clinical features suggestive of acute appendicitis were included after obtaining informed written consent. Inclusion criteria: • Patients aged 18 years and above presenting with clinical features suggestive of acute appendicitis. • Patients undergoing appendicectomy based on clinical assessment and surgical decision. • Patients willing to provide written informed consent. • Patients with available histopathological examination reports of the appendix specimen. Exclusion criteria: • Patients with previously diagnosed chronic appendicitis or recurrent appendicular symptoms. • Patients with appendicular mass or appendicular abscess managed conservatively. • Patients with previous appendicectomy. • Patients with severe comorbid illness contraindicating surgery. • Pregnant patients. • Patients unwilling to participate or lost to follow-up. All patients presenting with suspected acute appendicitis were evaluated through detailed clinical history, physical examination, and laboratory investigations. Demographic details including age and gender, clinical symptoms such as migration of pain, anorexia, nausea, vomiting, fever, and duration of symptoms were recorded. Abdominal examination findings, including right iliac fossa tenderness, rebound tenderness, and guarding, were documented. Routine laboratory investigations including complete blood count, total leukocyte count, differential leukocyte count, neutrophil percentage, and C-reactive protein levels were performed. Ultrasonography of the abdomen was performed whenever indicated to support clinical assessment. At the time of admission, each patient was assessed using both the AIR score and Alvarado score. The AIR score was calculated based on vomiting, right lower quadrant pain, rebound tenderness or muscular defense, white blood cell count, neutrophil proportion, and C-reactive protein levels. The Alvarado score was calculated based on migration of pain, anorexia, nausea/vomiting, right lower quadrant tenderness, rebound tenderness, fever, leukocytosis, and neutrophilia. Patients were categorized into low, intermediate, and high-risk groups according to the respective scoring criteria. Patients with clinical and radiological findings suggestive of acute appendicitis underwent appendicectomy through an open or laparoscopic approach based on clinical condition and surgeon preference. Intraoperative findings such as inflamed appendix, perforation, gangrenous changes, abscess formation, and other pathological findings were documented. The resected appendix specimens were sent for histopathological examination, which was considered the gold standard for confirmation of acute appendicitis. Histopathological findings were compared with AIR score and Alvarado score results to determine diagnostic accuracy. The parameters assessed included sensitivity, specificity, positive predictive value, negative predictive value, diagnostic accuracy, and correlation of both scoring systems with histopathological diagnosis. Patient outcomes, including postoperative complications and duration of hospital stay, were also recorded. All collected data were entered into a structured proforma and analyzed statistically. The collected data were analyzed using appropriate statistical methods. Continuous variables were expressed as mean ± standard deviation, and categorical variables were presented as frequencies and percentages. The Chi-square test was used for categorical variables, while independent t-test was used for comparison of continuous variables. Diagnostic performance was assessed using sensitivity, specificity, predictive values, and accuracy calculations. A p value <0.05 was considered statistically significant.

The majority of patients belonged to the 21–30 years age group, comprising 18 (32.14%) patients, followed by the 31–40 years age group with 16 (28.57%) patients. Acute appendicitis was predominantly observed among young adults. (Table 1) Male predominance was observed in the study population, with 34 (60.71%) male patients compared with 22 (39.29%) female patients. The male-to-female ratio was approximately 1.5:1. Table 1: Distribution of Subjects According to Age Group (n=56) Age group (years) Number Percentage (%) 18–20 8 14.29 21–30 18* 32.14 31–40 16 28.57 41–50 9 16.07 >50 5 8.93 Total 56 100 Histopathological examination confirmed acute appendicitis in 50 (89.29%) patients, while 6 (10.71%) patients had no evidence of acute inflammation. Histopathology was considered the reference standard for evaluating the diagnostic accuracy of scoring systems. Table 2: Distribution According to Histopathological Diagnosis Histopathological finding Number Percentage (%) Acute appendicitis present 50* 89.29 Normal appendix 6 10.71 Total 56 100 High-risk AIR scores were observed in 26 (46.43%) patients, followed by intermediate-risk scores in 22 (39.29%) patients. Majority of patients with confirmed appendicitis had higher AIR score categories. (Table 3) Table 3: Distribution According to AIR Score Category AIR score category Number Percentage (%) Low risk (0–4) 8 14.29 Intermediate risk (5–8) 22 39.29 High risk (9–12) 26* 46.43 Total 56 100 High probability Alvarado scores were observed in 27 (48.21%) patients, indicating that nearly half of the study population had strong clinical evidence suggestive of acute appendicitis. (Table 4) Table 4: Distribution According to Alvarado Score Category Alvarado score category Number Percentage (%) Low probability (<5) 9 16.07 Intermediate probability (5–6) 20 35.71 High probability (≥7) 27* 48.21 Total 56 100 Patients with histopathologically confirmed acute appendicitis demonstrated significantly higher AIR and Alvarado scores compared with patients having a normal appendix. Both scoring systems showed significant correlation with final histopathological diagnosis. (Table 5) Table 5: Comparison of Mean AIR Score and Alvarado Score According to Histopathological Diagnosis Histopathological diagnosis Number Mean AIR Score ± SD Mean Alvarado Score ± SD Acute appendicitis (n=50) 50 7.1 ± 1.6* 7.6 ± 1.5* Normal appendix (n=6) 6 4.2 ± 1.1 5.0 ± 1.2 p value <0.001 0.002 The AIR score demonstrated higher sensitivity, specificity, and overall diagnostic accuracy compared with the Alvarado score. This indicates that AIR scoring provided better discrimination between patients with and without acute appendicitis. Table 6: Diagnostic Accuracy of AIR Score and Alvarado Score for Acute Appendicitis Diagnostic parameter AIR Score Alvarado Score Sensitivity (%) 92.00 86.00 Specificity (%) 83.33 66.67 Positive predictive value (%) 97.87 94.51 Negative predictive value (%) 55.56 44.44 Diagnostic accuracy (%) 91.07 83.93

The study population predominantly comprised young adults, with 18 (32.14%) patients aged 21–30 years and 16 (28.57%) aged 31–40 years. There was a male predominance, with 34 (60.71%) males and 22 (39.29%) females. Histopathological examination confirmed acute appendicitis in 50 (89.29%) patients, while 6 (10.71%) had a normal appendix. In the present study, both scoring systems showed significant associations with histopathological diagnosis. The mean AIR score was significantly higher among patients with confirmed appendicitis than those with a normal appendix (7.1 ± 1.6 vs. 4.2 ± 1.1; p<0.001). Similarly, the mean Alvarado score was significantly higher in confirmed appendicitis (7.6 ± 1.5 vs. 5.0 ± 1.2; p=0.002). This indicates that increasing scores in both systems were associated with a greater likelihood of true appendicitis. Similar findings were reported by Manocha P et al.12 who observed mean AIR and Alvarado scores of 4.96 and 5.41, respectively, among patients evaluated for suspected appendicitis, supporting the usefulness of both scores for preoperative risk assessment. The AIR score demonstrated better overall diagnostic performance than the Alvarado score in the present study. AIR showed a sensitivity of 92.00%, specificity of 83.33%, PPV of 97.87%, NPV of 55.56%, and diagnostic accuracy of 91.07%, whereas Alvarado showed sensitivity of 86.00%, specificity of 66.67%, PPV of 94.51%, NPV of 44.44%, and accuracy of 83.93%. Thus, AIR provided better discrimination, particularly with respect to sensitivity and specificity. These findings are comparable with those of Karki OB et al.13 who reported sensitivity of 96.91% for AIR compared with 94.30% for Alvarado. They also observed higher PPV and NPV with AIR (79.70% and 72.20%) than with Alvarado (74.87% and 50%), with a superior AUC for AIR (0.701 vs. 0.580). Similarly, Kareem Z et al.14 reported a sensitivity of 92.55% for AIR compared with 60.64% for Alvarado and diagnostic accuracies of 91% and 63%, respectively. Although Alvarado showed higher specificity in their study, AIR demonstrated better sensitivity and NPV. The diagnostic accuracy of AIR in the present study (91.07%) was almost identical (91%), further supporting the greater overall discriminatory ability of AIR. The findings are also consistent with Jose T et al.15 who reported AUC values of 0.901 for AIR and 0.821 for Alvarado. At appropriate cut-offs, AIR demonstrated sensitivity of 98% and specificity of 97%, compared with 72% and 79%, respectively, for Alvarado. The superior performance was attributed to the incorporation of CRP and graded inflammatory parameters in AIR. In the present study, the higher specificity of AIR (83.33%) compared with Alvarado (66.67%) similarly suggests that AIR may better distinguish true appendicitis from non-appendicitis. Malyar AA et al.16 also demonstrated better discriminatory ability of AIR across different demographic groups, with AUC values of 0.87 in males and 0.89 in females compared with 0.64 and 0.69, respectively, for Alvarado. At a score greater than 4, AIR had higher sensitivity (0.97 vs. 0.83) and specificity (0.77 vs. 0.73). These findings are consistent with the present study, in which AIR demonstrated higher sensitivity and specificity than Alvarado. The better performance of AIR may be particularly useful in patients in whom clinical diagnosis is difficult. Risk stratification further demonstrated the usefulness of both systems in the present study. All 26 (100.0%) patients categorized as high risk by AIR had histopathologically confirmed appendicitis, while 20 (90.91%) of the intermediate-risk patients were confirmed cases. A significant association was observed between AIR categories and final diagnosis (p<0.001). Similarly, 28 (96.30%) patients classified as high probability by Alvarado had confirmed appendicitis, with a significant association between score category and histopathological diagnosis (p=0.003). These findings indicate that both scoring systems can effectively stratify patients according to the probability of acute appendicitis. The high-risk performance of AIR in the present study differs somewhat from the findings of Vaziri M et al.17 who reported that neither AIR nor Alvarado reliably distinguished high-risk pediatric patients, with sensitivity and specificity below 50%. However, in their low-risk group, AIR performed better, with sensitivity and specificity of 95% and 74%, compared with 90% and 70% for Alvarado. The difference may be explained by variation in patient age and clinical characteristics, as the present study predominantly included young adults rather than children. The present study demonstrated a strong positive correlation between AIR and Alvarado scores among patients with confirmed appendicitis (r=0.78, p<0.001). This indicates that both systems assess several common clinical features associated with acute appendicitis. However, the better diagnostic performance of AIR suggests that its incorporation of inflammatory markers and graded assessment may provide additional discriminatory value. Safaee M et al.18 similarly reported superior performance of AIR, with sensitivity, specificity, PPV and NPV of 96.1%, 82.3%, 97.0% and 77.7%, respectively, compared with 89.3%, 23.5%, 89.3% and 35.2% for Alvarado at the lower cut-off. The AUC was also higher for AIR (0.81 vs. 0.72). The findings regarding intermediate-risk patients require careful interpretation. Jose T et al.15 reported low sensitivity for both systems, with Alvarado performing slightly better than AIR (45% vs. 30%), although both demonstrated a PPV of 100%. They noted that elevated CRP levels among intermediate-risk patients could improve diagnostic interpretation. Similarly, Manocha P et al.14 reported considerably lower sensitivity for AIR (60.29%) and Alvarado (29.4%), although AIR remained more accurate (62.65% vs. 37.35%). These variations demonstrate that diagnostic performance can be influenced by patient selection, disease prevalence, score cut-offs, and the proportion of histologically confirmed disease. The present study therefore supports the use of AIR as a useful clinical prediction tool in suspected acute appendicitis. Its sensitivity of 92.00%, specificity of 83.33%, PPV of 97.87%, NPV of 55.56%, and diagnostic accuracy of 91.07% were superior to the corresponding values for Alvarado. The high proportion of histopathologically confirmed cases among patients in the high-risk categories of both scoring systems further supports their role in clinical risk stratification. However, the relatively modest NPV indicates that a low score alone may not be sufficient to exclude appendicitis in every patient.

The AIR score demonstrated superior diagnostic accuracy with higher sensitivity, specificity, and overall accuracy. The incorporation of inflammatory markers in the AIR score provides better risk stratification and assists in identifying patients requiring surgical intervention. Routine use of clinical scoring systems, particularly AIR scoring, may support early diagnosis, reduce unnecessary appendicectomies, and improve decision-making in patients presenting with suspected acute appendicitis. FINANCIAL SUPPORT AND SPONSORSHIP Nil. CONFLICTS OF INTEREST There are no conflicts of interest

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