Histological and clinical predictors of early and late renal outcome in ANCA-associated vasculitis

AbstractBackground. Renalinvolvementremainsamajordeter-minant in antineutrophil cytoplasmic autoantibody-associated small vessel vasculitis (AASV). While somepatients may develop persistent renal damage, othershave a favourable outcome.Methods. To identify patients at risk for poor renaloutcome, we evaluated 95 renal biopsies (67 initialbiopsies and 28 repeat biopsies) of 67 patients withAASV for the presence and extent of active (AI)and chronic (CI) lesions, retrospectively. AI, CI, levelsof proteinuria and dose of cyclophosphamide (CYC)were related to renal outcome.Results. Recovery of renal function in patients ini-tially dialysis dependent was associated with a lowerCI compared with patients who remained on dialysis(P<0.001), while AI did not differ significantly.In these patients, age <65 years revealed a positivepredictive value of 85% for renal function recovery.Patients initially requiring dialysis exhibited a higherAI and CI compared with those who did not. Renalfunction in long-term follow-up correlated with CIand the amount of proteinuria. This relationshipincreased with time, exhibiting at 4 years a correlationcoefficient of 0.607 for CI (P<0.01) and of 0.775 forproteinuria (P<0.001). Follow-up biopsies showed amore pronounced CI compared with initial biopsies(P<0.001). None of the investigated initial parameterswas predictive for renal relapse. However, there wasa relationship between dose and duration of CYC andtime to relapse. Compared with the initial biopsy,repeat biopsies of eight patients with a creeping serumcreatinine in clinical remission showed a decrease of AI(P<0.001) while CI increased rapidly. These patientsalso had less initial CYC (NS).Conclusions. These data suggest that in AASV, eval-uation of renal histopathology is helpful in predic-ting early and late renal outcome. Chronicity andproteinuria were the best determinants of poor renalprognosis. Activity may regress under therapy, whilechronicitymay progressdespitetreatment. Theamountof CYC seems to influence the occurrence of earlyrelapses and renal survival.Keywords: ANCA; follow-up biopsies;glomerulonephritis; histopathology; prognosis;therapy