Absence of antineutrophil cytoplasmic antibodies in giant cell arteritis.

OBJECTIVE

To determine the prevalence of antineutrophil cytoplasmic antibodies (ANCA) in patients with active giant cell arteritis (GCA).

METHODS

23 patients with GCA were selected according to ACR 1990 criteria. Sera were harvested in all patients at an active stage of the disease and during followup (1 to 3 sera/patient for a total of 50 sera). ANCA positivity was searched for by indirect immunofluorescence (IIF) and enzyme linked immunosorbent assay (ELISA) using a neutrophil extract, and antigen specificity was determined by proteinase 3 (PR3), lactoferrin (LF) and myeloperoxidase (MPO) ELISA:

RESULTS

Only 1/23 patients exhibited reactivity in IgG ANCA ELISA and IIF, with borderline anti-MPO reactivity in ELISA which was not inhibited by preincubation with MPO in the liquid phase, and no reactivity in Western blot analysis. Specificity could not be demonstrated in another patient who had positive IgG ANCA ELISA but negative ANCA IIF and negative antigen specific ELISA: All other patients were ANCA negative.

CONCLUSION

As our patients with GCA did not exhibit typical ANCA when validated antigen specific assays were used, careful laboratory controls and clinical evaluation would seem essential in cases of apparent ANCA positivity.