Inclusion of C-Reactive Protein and White Blood Cell Count in Diagnostic Workup of Patients with Clinically Suspected Appendicitis Stratifies for Imaging

Objectives: The aim of this retrospective study was to clarify whether plasma markers that are routinely used in the workup of patients suspected for acute appendicitis (AA) can stratify for imaging in both adults and children. Methods: A total of 1388 patients suspected of AA between January 2008 and till 2012 were included. CRP and WBC concentrations were retrospectively abstracted from the electronic health record. Receiver operating characteristic (ROC) curves were used to assess the diagnostic accuracy for the tests and to determine the best cutoff points. Results: In total 432 (22.4%) patients had histopathologically proven AA of whom 45 patients (10.4%) had perforated appendictis. The area under the curve (AUC 95% confidence interval [CI]) was 0.74 (95% CI = 0.70 to 0.77) for CRP and 0.74 (95% Cl = 0.71 to 0.78) for WBC both in adults and children. No cut off points had high enough sensitivity and specificity to accurately diagnose (perforated) AA. However, a high sensitivity of 91% was shown at cut-off 7.5x109/L WBC for AA (both in adults and children). In total 244 (18%) had a cut-off < 7.5×109/L. Those patients could have been sent home. Only 21 (5%) patients would have been missed in the AA group and 1(0.5%) patient in the perforated appendicitis group. Conclusions: None had clinical relevant cutoff points that could accurately discriminate between AA and other pathology, neither perforated appendicitis. However, WBC < 7.5×109/L for AA can identify a subgroup of 245 out of 1388 (18%) patients that could have been sent home without further imaging.