BIVARIATE ANALYSIS OF DIAGNOSTIC ACCURACY OF COMPUTER TOMOGRAPHY IN ACUTE APPENDICITIS

Purpose: Diagnosis of acute appendicitis is still a major problem. There are reports of error rates up to 25 %, despite considerable improvements in history –taking, clinical examination, and special tests and investigations. The aim of this study was to assess diagnostic value and to determine diagnostic accuracy of computer tomography (CT) in patients in whom acute appendicitis is suspected.

Methods: A literature search with predefined keywords and selection criteria was performed in Medline and Cochrane Library (1998 – 2005) and reference lists were hand-searched. Two researchers independently assessed the quality of the diagnostic trials with a standardized score and extracted the data from the trials which met the inclusion and exclusion criteria. If they disagreed, a third expert was consulted. Then a meta-analysis of the included trials was performed. A bivariate analysis [1] was used in order to account for the twodimensional character and possible negative correlation of sensitivity and specificity to determine overall sensitivity and specificity.

Results: The search identified 86 trials with a total of 12369 patients, but only 20 of them had the highest evidence level 1. The pooled sensitivity and specificity were 93.7 % (92.2 % - 95.0 %) and 90.7 % (87.5 % - 93.2 %), respectively, the 95 % confidence intervals are given in parantheses. Subgroups of trials with excellent quality scores or publications in journals with high impact factors (greater 3) gave similar results for diagnostic accuracy. Comparison of focused and nonfocused CT scans showed that focused CT had a significantly higher specificity with identical sensitivity.

Conclusion: This meta analysis showed a good performance of CT for acute appendicitis. Formerly published meta analyses did not use the bivariate model, and did not consider the twodimensional character of sensitivity and specificity but gave similar performance data.

[1] Reitsma JB et al.: Bivariate analysis of sensitivity and specificity produces informative summary measures in diagnostic reviews. J Clin Epidemiol, 2005. 58(10):982-90.