Twenty-two studies (3,436 patients) were included.
The cut-off value for CRP varied from 5 to 25 mg/L. The sensitivity ranged from 0.40 to 0.99 and the specificity from 0.27 to 0.90. The pooled sensitivity was 0.62 and the pooled specificity was 0.66 (confidence intervals not reported).
Effect of patient characteristics on the diagnostic accuracy: studies of suspected patients had a significantly better mean value for D (2.408) than patients selected for appendicitis (D=1.060), (P=0.016, unpaired samples).
Comparison of the diagnostic accuracy of leucocyte count (13 studies) and CRP: the diagnostic accuracy of leukocyte count was statistically significantly better than CRP; the mean D was 2.008 for leukocytes versus 1.529 for CRP (P=0.04, paired samples).
It was not possible to assess the influence of other variables due to the small number of studies.