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 acute 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) indicated less diagnostic accuracy. The best cut-off values were associated with 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 protein (CRP) concentration were independent predictors of acute appendicitis with cut-off values of >12.3x10(9)/L and >0 mg/L, respectively, but AUC values of over 0.5 were observed only in patients between 13 and 40 years of age.

CONCLUSION: Inflammatory variables added information of limited value in the diagnosis of suspected acute appendicitis. The test results should be interpreted differently in different groups of patients.