Sensitivity of interleukin-6 and C-reactive protein concentrations in the diagnosis of acute appendicitis.

Objective: To evaluate the interleukin-6 (IL-6) concentration in the diagnosis of acute appendicitis, either as a single or four-hourly test.
Design: Open study.
Setting: Teaching hospital, Sweden.
Subjects: 165 consecutive patients admitted with suspected acute appendicitis.
Main Outcome Measures: Correlation of concentrations of IL-6 and C-reactive protein with white cell count, duration of symptoms, and histological appearance of the appendix.
Results: Of 165 patients, 101 patients had their appendices removed, and of these 86 had histologically confirmed appendicitis. An IL-6 concentration of less than 15 ng/l was accepted as the reference. On admission IL-6 concentrations above 15 ng/l gave a sensitivity of 66% and a specificity of 31% for acute appendicitis. Repeated tests were of no value. When the patients operated on were divided in groups depending on the duration of symptoms, C-reactive protein was the most valuable test after 24 hours' abdominal pain. Total white cell count has the most sensitive in patients with abdominal pain of less than 24 hours' duration.
Conclusions: Measurement of IL-6 concentrations does not increase the accuracy of the diagnosis of acute appendicitis. There was no significant correlation between IL-6 and C-reactive protein concentrations.