ANCA in dialysis patients: a role for bioincompatibility?

Background. Anti-neutrophil cytoplasmic autoantibodies (ANCA) have been described in patients suffering from systemic vasculitis such as Wegener granulomatosis, microscopic polyangiitis, Churg-Strauss syndrome and other pathological conditions. in this paper we report a greater incidence of ANCA in hemodialysis patients as compared to peritoneal dialysis patients, predialytic uremic patients and non-renal patients; a possible role for dialysis bioincompatibility in ANCA generation was also investigated. Methods. A total of 335 uremics in substitutive treatment (176 in hemodialytic treatment and 159 in peritoneal dialysis) were examined for ANCA positivity. A total of 189 patients with advanced renal failure in conservative treatment and 100 healthy subjects were used as control. The dialysis techniques were standard hemodialysis (n = 119), low volume hemodiafiltration (n = 26) and hemofiltration (n = 31). ANCA positivity was examined by immunofluorescence (IF): diffuse finely granular staining was considered as classical positive reaction (C-ANCA) and P-ANCA was diagnosed if a perinuclear staining was observed. EIA for proteinase-3 (anti PR-3) and myeloperoxidase-antibodies (anti-MPO) were also performed. Results. In non-renal patients and in patients with pre-dialytic renal insufficiency none were found ANCA positive, in peritoneal dialysis patients all but one were ANCA negative with IF; with all EIA test resulting negative. In hemodialytic patients, a positive IF test was found in 26 (14.7%) for P-ANCA and in 5 (2.8%) for C-ANCA; using the EIA test 23 (13%) patients were positive for MPO and 12 (6.8%) for PR-3. Conclusions. No correlation with age, primary renal diseases, dialytic age, dialysis membrane materials was found; regarding the different extracorporeal dialytic techniques a higher incidence (p < 0.02) was detected in patients undergoing HDF. Backfiltration of contaminated dialysate may induce ANCA via an increased cytokine generation.