Clinical Value of the Total White Blood Cell Count and Temperature in the Evaluation of Patients with Suspected Appendicitis

Abstract

The total white blood cell (WBC) count and temperature are often expected to be elevated in patients with appendicitis. Clinicians often use the results of these parameters in making a judgment about the presence or absence of disease. The objective of this study was to assess the discriminatory value of the total WBC count and presenting body temperature in patients presenting to the emergency department (ED) with signs and symptoms suggestive of appendicitis. This was a prospective consecutive case series in a university ED with an annual census of 38,000. All patients presenting to the ED in whom the diagnosis of appendicitis was the attending physician's primary consideration were enrolled. Measures included age, gender, symptoms, physical findings, patient temperature as taken in the ED, initial total WBC count, and discharge diagnosis. Admitted patients were followed up until surgical or clinical outcomes, and discharged patients were followed up by telephone two weeks after the initial visit. All statistical analysis was performed using StatsDirect version 1.9.8. A total of 293 patients were enrolled over a two-year study period. The total WBC count was measured in 274 cases, and the temperature was measured in 293 cases. There were 130 male patients and 163 female patients. The mean age of the patients was 30.8 years (range, 7-75 years). Appendicitis was confirmed in 92 patients. In this study group of patients, a total WBC count >10,000 cells/mm(3) had a sensitivity of 76% (95% confidence interval [95% CI] = 65% to 84%) and a specificity of 52% (95% CI = 45% to 60%). The positive predictive value (PPV) was 42% (95% CI = 35% to 51%), and the negative predictive value (NPV) was 82% (95% CI = 74% to 89%). The positive likelihood ratio (LR) was 1.59 (95% CI = 1.31 to 1.93), and the negative LR was 0.46 (95% CI = 0.31 to 0.67). A temperature >99.0 degrees F had a sensitivity of 47% (95% CI = 36% to 57%) and a specificity of 64% (95% CI = 57% to 71%). The PPV was 37% (95% CI = 29% to 46%), and the NPV was 72% (95% CI = 65% to 79%). The positive LR was 1.3 (95% CI = 0.97 to 1.72), and the negative LR was 0.82 (95% CI = 0.65 to 1.01). The areas under the curve for the receiver-operating characteristic (ROC) curve were 0.72 (95% CI = 0.65 to 0.79) and 0.59 (95% CI = 0.52 to 0.66) for an elevated total WBC count and an elevated temperature, respectively. An elevated total WBC count >10,000 cells/mm(3), while statistically associated with the presence of appendicitis, had very poor sensitivity and specificity and almost no clinical utility. There was minimal statistical association between a temperature of >99 degrees F and the presence of appendicitis. The ROC curve suggests there is no value of total WBC count or temperature that has sufficient sensitivity and specificity to be of clinical value in the diagnosis of appendicitis. Clinicians should be wary of reliance on either elevated temperature or total WBC count as an indicator of the presence of appendicitis.