Appropriateness of antineutrophil cytoplasmic antibody testing in a tertiary hospital

Aims: To determine whether indications for ordering antineutrophil cytoplasmic antibodies (ANCA) meet the 1999 guidelines proposed for ANCA testing; and to examine the test characteristics of the ANCA test. Methods: The indications for all ANCA tests over a two-year period were assessed and compared to the 1999 guidelines for the appropriate testing of ANCA. Results: 1127 tests were examined. Overall 33.4% had an indication meeting the 1999 guidelines. The commonest non-guideline indications were ocular or orbital inflammation, liver disease and inflammatory bowel disease. All tests with a positive ANCA had indications for testing in line with the 1999 guidelines. In all but one case an ANCA associated small vessel vasculitis (AASVV) was present. Conclusions: ANCA is ordered for a wide range of guideline and non-guideline indications. No cases of AASVV would have been missed if ordering were restricted to tests meeting the 1999 guidelines.