Diagnostic value of C-reactive protein in suspected acute appendicitis - A prospective case control study.

ABSTRACT

Aim: To find out the Sensitivity, Specificity and Predictive value of C-reactive protein in the diagnosis of acute appendicitis. Materials and Methods: Hundred patients undergoing emergency appendicectomy were cases and thirty patients undergoing interval appendicectomy during the same period were controls. Creactive protein was measured pre-operatively. Results: CRP was reactive in 89% of cases and 3 of 30 controls (P = 0). Among the thirteen complicated cases, two had a CRP reactivity of 1.2 mg/dl, eight had 2.4 mg/dl and three had 3.6 mg/dl. In the uncomplicated cases, forty nine were reactive at 1.2 mg/dl, twenty six at 2.4 mg/dl and one at 3.6 mg/dl ( P = 0.0009). In histopathologically inflamed appendix, reactivity was 94.4% and in normal appendix reactivity was 40% ( P = 0.00007). CRP positivity had a sensitivity of 94.4% (CI 89.9-98.9) and a positive predictive value of 95.5% (CI 91.4-99.6). CRP reactivity and leucocytosis if combined, the sensitivity, specificity, PPV and NPV were 85%, 100%, 100% and 81% respectively. Threshold for CRP reactivity if raised to 2.4 mg/dl, the sensitivity, specificity, PPV and NPV are 42%, 100%, 100% and 16% respectively. Conclusion: CRP estimation is a good 'rule-in' test and not-so-good 'rule-out' test to diagnose acute appendicitis.