European Journal of Cardiovascular Medicine

Acute appendicitis represents one of the most frequent causes of an acute surgical abdomen, with a lifetime incidence estimated at 8.6% for men and 6.7% for women.(1) The complication rate varies between 5.5% and 11%, and reported mortality ranges from 0.09% to 1.8%.(2–5) Negative appendectomy rates can reach 18.2% overall and may approach 28.7% in women of childbearing age.(6) Despite advances in diagnostic methods, achieving an accurate clinical diagnosis remains difficult, particularly in reproductive-age females and at the extremes of age, due to atypical presentations.(7) If not treated promptly, uncomplicated appendicitis can progress to perforation, substantially increasing morbidity and mortality. Consequently, surgeons often operate even when the diagnosis is not absolutely certain.(8) Many are willing to accept negative appendectomy rates up to 30%, which increases costs and exposes patients to unnecessary surgery despite the availability of imaging modalities. The ideal approach is to minimise both negative appendectomies and perforations, without compromising patient safety.

Several clinical scores—such as the Modified Alvarado Score (MAS) and the Appendicitis Inflammatory Response Score (AIRS)—and imaging modalities including computed tomography (CT), magnetic resonance imaging (MRI) and ultrasonography (USG) have been developed to assist diagnosis. CT abdomen offers high diagnostic performance (sensitivity 98.5%, specificity 98%, NPV 99.5%, PPV 93.9%) but is neither inexpensive nor universally accessible. By contrast, ultrasound is widely available, rapid to perform, and has a reported visualisation rate between 22% and 98%.(9) MAS itself shows a sensitivity of 82.8%, specificity of 56%, PPV of 89.3%, and NPV of 42.4%.(10)

Multiple studies have suggested ultrasound as an adjunct when clinical scoring is inconclusive.(11) For example, Agrawal et al.(12) combined MAS and USG and demonstrated a sensitivity of 99.1%, specificity of 72.7%, PPV of 97.2%, NPV of 88.9% and accuracy of 96.6% in diagnosing acute appendicitis. This combined approach may be especially valuable in resource-limited settings, where decisions often rely on limited investigations and clinical evaluation.

This prospective analytical study was undertaken in the Department of Surgery at a tertiary care hospital over an 24-month period, from January 2023 to December 2024, to assess the diagnostic performance of the Combined Modified Alvarado Score (MAS) in acute appendicitis. The sample size was calculated as 110 based on an expected sensitivity of 96.6%, 95% confidence interval, and a 10% allowance for attrition.(12)

All patients clinically suspected of having acute appendicitis and undergoing emergency appendectomy were included. Exclusion criteria were patients presenting with appendicular abscess or mass, perforation with peritonitis requiring laparotomy, age under 14 years, appendiceal neoplasm, or those managed conservatively. Ethical clearance was obtained from the Institutional Review Committee, and the study conformed to STROCSS guidelines and the Declaration of Helsinki.13

Data were collected on a structured pro forma covering relevant clinical variable. At presentation, each patient’s detailed history was recorded, particularly regarding pain, nausea, anorexia and vomiting, and a focused physical examination was performed, noting features such as fever, tenderness and rebound tenderness in the right iliac fossa (RIF). Blood investigations included total and differential leukocyte counts.

Ultrasound was performed using a PHILIPS machine with a 5–12 MHz linear probe. Preoperative MAS and USG scores were calculated for each patient according to predefined parameters. A MAS <7 was considered negative and ≥7 positive for acute appendicitis.14 Histopathological examination served as the gold standard.

MAS scores of 1–4 (unlikely), 5–6 (probable) and 7–9 (definite) were coded as 1, 2 and 3 respectively. USG findings were similarly categorised as unlikely, probable and definite with scores of 1, 2 and 3.15 The Combined MAS was derived by summing the two scores: totals of 1–2 indicated “unlikely,” 3–4 “probable” and 5–6 “definite” appendicitis. For diagnostic testing, combined scores of 3–6 (probable/definite) were considered positive and scores 1–2 negative.

Data were entered and analysed with EPI-INFO software. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and overall accuracy were calculated for MAS, USG and Combined MAS using standard formulae. Infiltration of the muscularis propria by neutrophils on histopathology was considered diagnostic of acute appendicitis.12 A p-value <0.05 was taken as statistically significant.

A total of 110 patients with a clinical diagnosis of acute appendicitis underwent emergency open appendectomy. Histopathological examination confirmed acute appendicitis in 100 cases (90.9%), while 10 cases (9.1%) were negative, indicating false-positive clinical diagnoses. The cohort included 56 females (50.9%) and 54 males (49.1%), with a median age of 30 years. The most common presenting sign was right iliac fossa tenderness (90.9%), followed by leucocytosis (75%), whereas fever was least frequent (7.3%).

When classified by MAS, 28 patients (25.5%) fell into the “unlikely” category (scores 1–4), 40 (36.4%) into “probable” (scores 5–6), and 42 (38.1%) into “definite” (scores 7–9). In total, 68 cases (61.9%) were MAS-negative (scores <7) and 42 MAS-positive (scores ≥7). Comparing MAS to histopathology, MAS correctly identified 42 of the 100 true cases of appendicitis (Table 2). Sensitivity, specificity, PPV, NPV and overall accuracy were 42%, 100%, 100%, 20.8% and 47.27%, respectively.

Table 1 showing Combined MAS test (modified Alvarado score and USG score)

Table 2: Comparison of MAS, USG, combined test with HPE

*Data do not fulfil the assumption for application of the χ2 test as the cell value is 0.

Table 3: Combined MAS test and score

Ultrasound diagnosed 82 patients (74.5%) as definite appendicitis, 8 (7.3%) as probable and 20 (18.2%) as unlikely. Overall, 90 patients (81.8%) were classified as positive for appendicitis by USG. Among these, 6 were false positives compared with histopathology, and among the 20 USG-negative cases, 16 were histologically proven appendicitis (Table 2). Consequently, ultrasound achieved a sensitivity of 84%, specificity of 40.0%, PPV of 93.3%, NPV of 20% and accuracy of 80%.

Combining MAS and USG scores produced 60 patients (54.5%) in the “definite” category (scores 5–6), 48 (43.6%) in “probable” (scores 3–4) and 2 (1.8%) in “unlikely” (scores 1–2). This resulted in 108 patients (98.2%) testing positive overall (Table 3). On comparison with histopathology, 98 of these 108 were true positives; five were false positives, and the single test-negative case was histologically positive (Table 2). The Combined MAS yielded a sensitivity of 98.18%, specificity of 0%, PPV of 90.7%, NPV of 0% and accuracy of 89.09%.

This study included 110 patients who underwent emergency appendectomy for suspected acute appendicitis; histopathology confirmed appendicitis in 90.9% of cases. MAS incorporates nine clinical and laboratory parameters. In our cohort, right iliac fossa tenderness (90.9%), leucocytosis (75%), rebound tenderness (67.3%) and migratory pain (56.4%) were the most frequent findings, consistent with previous work by Andersson et al.16 showing these features to be significantly associated with appendicitis.

We found MAS to have a sensitivity of 42% with no false positives, resulting in a specificity of 100%. PPV and NPV were 100% and 20.8%, and the overall accuracy was 47.2%. These values align with findings from Ahmed et al.(14) for sensitivity, specificity and PPV, although our NPV and accuracy were lower than reported by them, and closer to the lower values seen in the study by Kondoju et al.(17). Variation in MAS performance may reflect differences in sex distribution, clinical skill in eliciting signs or subject characteristics.

Ultrasound correctly identified 42 of 50 histologically proven cases (sensitivity 84%, specificity 40%, PPV 93.3%, NPV 20%, accuracy 80%). These results are similar to those reported by Nasiri et al.(18) and Narendra et al.(19) except for lower specificity. This reduced specificity may be attributable to operator dependence and factors such as patient body habitus, abdominal distension or female pelvic structures, which can obscure findings even for experienced radiologists. In our teaching hospital setting, USG was performed by different radiologists, including trainees, which likely reflects real-world conditions but may have contributed to variability.

Combining MAS and USG yielded a sensitivity of 98.18%, PPV of 90.7% and accuracy of 89.09%, but specificity and NPV were 0%. Our sensitivity, PPV and accuracy are comparable to other studies such as Kansakar et al.(9) and Kurane et al.(20) but the low specificity and NPV differ. This may be due to methodological differences. Kansakar et al.(9) defined the combined score simply as positive or negative, without including “probable” categories, while Nautiyal et al.(21) excluded cases managed conservatively from analysis, potentially inflating specificity. Our inclusion of all clinically operated cases may have reduced specificity.

Previous studies, such as those by Pipal et al.(22), have shown that adding imaging to clinical scoring improves diagnostic accuracy, a finding also observed here. Agrawal et al.(12) reported much higher specificity and NPV (63.6% and 87.5%), whereas our study produced lower values, likely due to small sample size and our specific scoring thresholds. Our data suggest that raising the cut-off for the combined score above two may improve specificity. We also excluded patients who were positive on MAS/USG but not operated clinically, which may have further lowered specificity and NPV.

Overall, our findings support the evidence that ultrasound increases the sensitivity and diagnostic yield of the MAS. In our cohort, combining MAS and USG achieved a sensitivity of 98.18% and accuracy of 89.09%, compared with MAS alone (42% and 47.27%) and USG alone (84% and 80%). A positive combined MAS strongly indicates appendicitis, but a negative combined MAS does not reliably exclude it, and further evaluation may be necessary.

Combining ultrasound with the Modified Alvarado Score significantly improves the sensitivity and diagnostic accuracy of clinical assessment for acute appendicitis. This combined approach may serve as a practical alternative to CT or MRI in settings where advanced imaging is limited. Using a combined scoring system can facilitate earlier diagnosis, reduce complications and assist in timely decision-making. However, larger studies are needed to validate this scoring system and to refine its cut-off points, particularly to improve specificity and negative predictive value.

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