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[Antineutrophil cytoplasmic autoantibodies in systemic vasculitis]
Jostein Skjalg Hagemo1, Knut Aasarød, Torolf Moen
1Norges teknisk-naturvitenskapelige universitet, 7489 Trodeim. jskjalg@online.no
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.