ANCA in haemodialysis patients

The prevalence of positive ANCA as well as the prevalence of PR-3 and MPO antibodies were examined in a cross-sectional sample of 1277 haemodialysis patients from 16 German haemodialysis centres. We found 32 patients positive for c-ANCA (median titre 1:40; range 1:20-1:320) and 65 for p-ANCA (1:80; 1:20-1:1280). Twenty-two percent of the c-ANCA-positive and 31% of the p-ANCA-positive patients had PR-3 and MPO antibodies by ELISA respectively. Clinical evidence of vasculitis was found in 11 of 32 c-ANCA-positive and 19 of 65 p-ANCA-positive patients. Of the 11 c-ANCA-positive, four had a known diagnosis of Wegener's granulomatosis (WG); WG was recognized after the test in a further five patients and two had renal limited RPGN. Of the 19 p-ANCA-positive patients, three had a clinical diagnosis of microscopic polyarteritis (MP), MP was newly diagnosed in a further 12, WG in one and renal limited RPGN in three. The patients had not received cyclophosphamide (the diagnosis had been non-specified 'systemic disease'). Thus false-positive ANCA, as defined by absence of vasculitis, was found in 5% of dialysis patients versus 0% in patients with preterminal renal failure (n = 152) or blood donors (n = 150). Patients with vasculitis tended to have higher c-ANCA and p-ANCA titres respectively, but there was a considerable overlap. Titres were not higher in patients symptomatic at the time of examination (6 of 11 c-ANCA and 10 of 19 p-ANCA), but PR-3 and MPO ELISA were positive in all but two.(ABSTRACT TRUNCATED AT 250 WORDS)