[Antineutrophil cytoplasmic autoantibodies in systemic vasculitis].

BACKGROUND

Antineutrophil cytoplasmic autoantibodies (ANCA) are directed against antigens located in the cytoplasm of neutrophil granulocytes and monocytes. Detection of ANCA has proved to be a useful diagnostic tool for a group of systemic vasculitis, especially Wegener's granulomatosis. Both indirect immunofluorescence (IIF) and ELISA have been used to detect ANCA.

MATERIAL AND METHODS

In this study, samples from 319 patients tested by both immunofluorescence and ELISA were evaluated; 27 of these were diagnosed with Wegener's granulomatosis.

RESULTS

The diagnostic sensitivity for Wegener's granulomatosis was 70% for C-ANCA and 63% for PR3-ANCA. The specificity was 97% and 99% respectively. Positive predictive value for the diagnosis of Wegener's granulomatosis in our population was 68% for C-ANCA and 90% for PR3-ANCA. Negative predictive value was 97% and 97% respectively.

INTERPRETATION

We recommend that immunofluorescence is used for screening when an ANCA-associated vasculitis is suspected. However, a number of antigen specificities can provide the immunofluorescence patterns, and for this reason we recommend PR3-ELISA and MPO-ELISA tests whenever the immunofluorescence test is positive.