Role of Serum C-Reactive Protein in Improving the Diagnostic Accuracy of the Modified Alvarado Score in Patients with Suspected Acute Appendicitis: A Cross-sectional Study

Abstract

Background: Acute appendicitis is a common surgical emergency; delayed diagnosis may increase morbidity, whereas diagnostic uncertainty may lead to unnecessary appendectomy. The Modified Alvarado Score (MAS) is widely used, but its performance may be limited in equivocal cases. Serum C-reactive protein (CRP) may provide complementary inflammatory information. Objective: To assess whether serum CRP improves the diagnostic performance of MAS in patients with suspected acute appendicitis, using histopathological findings as the reference standard. Methods: This hospital-based cross-sectional study included 223 consecutive patients aged ≥13 years who underwent appendectomy at Mymensingh Medical College Hospital, Bangladesh, from January 2022 to June 2023. MAS and qualitative serum CRP (>6 mg/L) were assessed preoperatively. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and overall diagnostic accuracy were calculated for MAS, CRP, and the combined criterion of MAS ≥7 with raised CRP. Results: Histopathological examination confirmed acute appendicitis in 209 patients (93.7%). MAS showed 84.69% sensitivity, 78.57% specificity, and 84.30% diagnostic accuracy. CRP showed 93.78% sensitivity, 64.29% specificity, and 91.93% diagnostic accuracy. The combined criterion showed 83.73% sensitivity, 85.71% specificity, 98.87% PPV, 26.09% NPV, and 83.86% diagnostic accuracy. Thus, CRP alone had the highest sensitivity and accuracy, whereas the combined criterion had the highest specificity and PPV. Conclusion: Serum CRP provides useful adjunctive information to MAS. A positive MAS-CRP combination may strengthen diagnostic confidence because of its high specificity and PPV; however, neither a low MAS nor a normal CRP result reliably excludes acute appendicitis.