Receiver operating characteristic analysis of leukocyte counts in operations for suspected appendicitis

There has been no clear-cut value of the white blood cell (WBC) count in differential diagnosis of acute appendicitis in emergency medicine. Therefore, the aim of this study was to assess the preoperative WBC counts in 3 groups of patients operated on for a clinical suspicion of acute appendicitis with different findings at appendectomy: uninflamed appendix, uncomplicated acute appendicitis, or complicated acute appendicitis.

The medical records of 540 patients who underwent appendectomy for suspected acute appendicitis during a 17-month period were retrospectively reviewed. Data for 3 groups of patients were analyzed to calculate the sensitivity and specificity of the WBC count in the diagnosis of acute appendicitis, and we calculated likelihood ratios for 2 cut-points with either high sensitivity or high specificity. Receiver operating characteristic curves were used to evaluate the WBC count in relation to the true diagnosis and severity of acute appendicitis.

We were able to identify patients with appendicitis on a statistically significant level using receiver operating characteristic curves of WBC counts (area under the curve = 0.756, P < .001), but the WBC count had no diagnostic value in differentiating between uncomplicated and complicated groups (area under the curve = 0.55, P = .086). Likelihood ratio ranged from 1.79 (95% confidence interval, 1.17-2.3) for WBC count of more than 10,500 cells/mm(3) to 3.20 (95% confidence interval, 2.72-3.24) for WBC count of more than 14,300 cells/mm(3).

White blood cell count is helpful in the diagnosis and exclusion of appendicitis. However, there is no value to differentiate advanced appendicitis.