OBJECTIVE To study the frequency and distribution of antineutrophil cytoplasmic autoantibodies (ANCA) among patients with reactive arthritis (ReA), rheumatoid arthritis (RA), and ulcerative colitis (UC) using different immunological methods.

RESULTS Sixteen per cent of patients with ReA were positive in immunofluorescence compared with 30% of patients with RA, and 70% of patients with UC. Thirty two per cent of patients with ReA were positive in ELISA. Antibodies directed against lactoferrin occurred in 20%, antibodies against bactericidal permeability increasing protein (BPI), elastase, cathepsin G, myeloperoxidase, and proteinase 3 were found in 8%, 2%, 2%, 8%, and 6%, respectively. Overall, 50% of RA sera and 53% of UC sera were positive in one or more ELISA assays, the corresponding figures for antibodies against individual antigens were for RA 7%, 3%, 0%, 13%, 47%, 17% and for UC 13%, 20%, 0%, 23%, 10%, and 17%. In immunoblotting, bands corresponding to lactoferrin and BPI were recognised in 44% and 22% of ReA sera.

CONCLUSION Antibodies against neutrophil granule antigens are often found in patients with ReA, primarily among those with chronic disease. The different methods detect various subsets of antibodies, with immunoblotting being the most and immunofluorescence the least sensitive.