Objectives: In spite of a strong positive association between ulcerative colitis and the presence of perinuclear anti-neutrophil cytoplasmic antibodies (p-ANCAs), the immunogenetic significance of these antibodies remains unclear. We studied patients with quiescent disease to clarify whether ANCAs are present even in the absence of inflammation.
Design: The prevalence of ANCAs was estimated blindly in 137 patients with ulcerative colitis, 128 of whom had quiescent disease with a mean duration of complete clinical and biochemical remission of 14 years. For comparison, we studied sera from 110 patients with Crohn's disease, 27 of whom had a low or intermediate grade of inflammatory activity. The mean duration of complete remission in these patients was 8.5 years.
Methods: ANCAs were detected using indirect immunofluorescence and enzyme-linked immunosorbent assays (ELISAs).
Results: Only 13 (9%) of 137 patients with ulcerative colitis had ANCAs (5% had p-ANCAs). Three patients had previously undergone colectomy. In patients with Crohn's disease, ANCAs were observed in 17 of 110 patients (15%, 6% had p-ANCAs). Fifteen of these patients had colonic disease.
Conclusion: In patients with ulcerative colitis free from inflammation for prolonged periods of time, ANCAs occurred less frequently than has previously been reported. Patients with Crohn's disease had the expected frequency of ANCA positivity, which for colonic Crohn's disease was comparable to that found in patients with ulcerative colitis. These findings suggest that the titre of ANCAs decreases with time in inactive disease and may be undetectable with conventional assays after several years of complete remission.