Evaluate Diagnostic Efficacy of Serum C-Reactive Protein Levels as a Marker for Predicting Acute Appendicitis.

Abstract

Background: Acute appendicitis is one of the most frequently encountered surgical emergencies, but the diagnosis can continue to be difficult due to variable clinical presentations and the inability to rely on any single laboratory test. The C-reactive protein (CRP) is an easily obtained and inexpensive inflammatory marker that could help identify patients with acute appendicitis. In the present study, the diagnostic performance of serum CRP was evaluated in comparison with histopathology as reference standard.

Objective: To determine the diagnostic accuracy of serum C-reactive protein levels for predicting acute appendicitis, taking histopathological examination as the gold standard.

Methods: This cross-sectional validation study was conducted in the Department of General Surgery, Rawalpindi Teaching Hospital, Rawalpindi, from 16 February 2026 to 16 June 2026. The patients of the study were 87, whose age range was 11-75 years and they were selected by the non-probability consecutive sampling technique with a presumed diagnosis of acute appendicitis. Pre-operative levels of serum CRP were analysed, and those levels >10 mgs /L were taken as positive. All patients had an appendectomy performed and the appendix were examined histopathologically. The sensitivity, specificity, positive predictive value, negative predictive value, diagnostic accuracy and receiver operating characteristic analysis were calculated.

Results: Histopathology confirmed acute appendicitis in 70 (80.5%) patients. At the predefined CRP cutoff of >10 mg/L, serum CRP demonstrated a sensitivity of 80.0%, specificity of 82.4%, positive predictive value of 94.9%, negative predictive value of 50.0%, and overall diagnostic accuracy of 80.5%. The area under the receiver operating characteristic curve was 0.862, indicating good discriminatory performance. The ROC-derived optimal cutoff was approximately 12.4 mg/L, with a sensitivity of 78.6% and specificity of 88.2%.

Conclusion: Serum CRP demonstrated good diagnostic performance in patients with suspected acute appendicitis, particularly because of its high positive predictive value. However, its relatively low negative predictive value indicates that a normal CRP level cannot reliably exclude appendicitis. CRP should therefore be interpreted alongside clinical evaluation, scoring systems, and appropriate imaging rather than being used as a standalone diagnostic test.