Background and purpose: Appendectomy is the most common emergency surgery and diagnosis of this clinical problem is of great importance in decreasing the complications and treatment costs. In this study the diagnostic value of bilirubin level and WBC count in acute appendicitis were compared.

Materials and methods: A cross-sectional study was performed in patients attending Emergency Department in Sari Imam Khomeini Hospital, 2014, with pain in abdomen and primary diagnosis of appendicitis. The diagnostic value of lab tests (bilirubin level and WBC count) was investigated. Also, the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of two tests were compared.

Results: The specificity, sensitivity, PPV, and NPV of hyperbilirubinemia for acute appendicitis was 66.7%, 75.8%, 95.8%, and 21.4%, respectively. The specificity and sensitivity of leukocytosis for appendicitis was 100% and 71.4%, respectively. The positive predictive value for an elevated WBC count was 100% and the negative predictive value was 25.7%.

Conclusion: Bilirubin level and WBC count were found to have fairly similar predictive values for acute appendicitis. Therefore, measuring bilirubin levels might be useful when investigating a patient with symptoms of acute appendicitis.