Diagnostic accuracy of inflammatory markers in patients operated on for suspected acute appendicitis: a receiver operating characteristic curve analysis

Objective: To analyse the diagnostic accuracy of inflammatory variables in patients operated on for suspected acute appendicitis. Design: Open prospective population based study. Setting: Teaching hospital, Norway. Interventions: Appendicectomy in 544 patients with clinically suspected acu te appendicitis. Main outcome measures: Diagnostic accuracy of inflammatory variables using receiver operating characteristic (ROC) curve analysis. Logistic regression model of inflammatory variables using results of ROC-analysis. Results: A small area under the ROC curve (AUC) (between 0.56 and 0.69) ind icated less diagnostic accuracy. The best cut-off values were associated wi th low sensitivity and specificity, varying from 46% to 88%. Age, duration of history, and histological grade of inflammation significantly influenced the test results (AUC > 0.5). The white cell count (WCC) and C-reactive pr otein (CRP) concentration were independent predictors of acute appendicitis with cut-off values of >12.3 x 10(9)/L and >0 mg/L, respectively, but AUC values of over 0.5 were observed only in patients between 13 and 40 years o f age. Conclusion: Inflammatory variables added information of limited value in th e diagnosis of suspected acute appendicitis. The test results should be int erpreted differently in different groups of patients.