Purpose: To summarize the literature on the clinical utility of antineutrophil cytoplasmic antibody (c-ANCA) as a diagnostic marker for Wegener granulomatosis.
Data sources: A structured literature search was done using MEDLINE; this search, combined with a manual search, yielded 747 articles for potential inclusion. These articles passed through a 4-stage review. Studies were included if they had a specified reference standard and a systematic method of patient selection and if a 2 x 2 contingency table could be constructed from their results. Fifteen articles met these criteria.
Data extraction: 3 physicians reviewed all selected articles. Detailed data abstraction was done, and the quality of the study methods was assessed. Items abstracted included the method of patient selection, the study design, the reference standard, the c-ANCA testing technique, disease activity, and the test results. Disagreements among reviewers were resolved by consensus. Contingency tables were used to calculate the operating characteristics for Wegener granulomatosis overall and for active and inactive Wegener granulomatosis.
Results: The sensitivities of c-ANCA testing for overall Wegener granulomatosis ranged from 34% to 92%, and the specificities ranged from 88% to 100%. The pooled sensitivity was 66% (95% CI, 57% to 74%), and the pooled specificity was 98% (CI, 96% to 99.5%). Four articles provided data on disease activity. For active disease, the pooled sensitivity was 91% (CI, 87% to 95%), and the pooled specificity was 99% (CI, 97% to 99.9%). For inactive disease, the pooled sensitivity and specificity were 63% and 99.5%, respectively.
Conclusions: Although c-ANCA test results may serve clinicians as adjunct evidence for the diagnosis of Wegener granulomatosis, these results must be viewed in the context of the patient's clinical picture and disease activity and the prevalence of Wegener granulomatosis in the clinical setting in which the patient is seen.