The accuracy of white blood cell count in the diagnosis of acute appendicitis using age-sex-adjusted receiver operating characteristic approach

Background: White blood cell (WBC) counts are commonly used for the diagnosis of acute appendicitis in the early stages of pain. However, the effect of certain confounders, particularly age and sex, has been less focused. The purpose of this study was to investigate the diagnostic accuracy of white blood cells in the prediction of acute appendicitis using age-sex-adjusted receiver operating characteristic (ROC) curve. Methods: In this cross sectional study, 131 patients who had undergone appendectomy were studied during 2010-2011. Patients were placed in the normal appendix and acute appendicitis groups. ROC regression was used to identify the effects of the variables of age and sex on the diagnostic accuracy of WBCs using the area under the ROC curve (AUC). Statistical analysis was conducted in Stata 12 software. Results: In ROC regression method, the AUC for the variable of WBC was 0.643 (95% CI: 0.555-0.725) without adjustment for age and sex variables, 0.672 (0.584-0.751) with an age-adjusted variable, 0.698 (0.612-0.775) with a sex-adjusted variable, and 0.710 (0.624-0.786) with both age-sex adjusted variables. Conclusion: Results indicated that age-sex adjusted variables increased the diagnostic accuracy of the WBC test for predicting acute appendicitis using ROC regression method for the WBC test.