IGA NEPHROPATHY - PROGNOSTIC CLASSIFICATION OF END-STAGE RENAL-FAILURE

Background. As yet, no clinical or morphological prognostic classifica tion of IgA nephropathy (IgAN) has been generally accepted. The object ive of our study was to quantify the risk of developing end-stage rena l failure (ESRF) in IgAN. Methods. We report a prospective longitudina l study of 210 patients with IgAN confirmed by biopsy between 1987 and 1991. Thirty-two (15.2%) patients were lost to follow-up. Mean follow -up after renal biopsy was 5.6 (SD = 2.6) years. The variables include d age, gender, illnesses prior to discovery of IgAN, clinical features at IgAN discovery, 24-h proteinuria, serum creatinine, IgA level, and antihypertensive drugs taken at the time of renal biopsy. Sixty-six r enal biopsies were classified by light-microscopy according to Lee's m orphological classification. The end-point was ESRF. Survival was anal ysed by a backward and forward stepwise procedure using the Cox model. The most accurate determination of relative risk was obtained by asse ssing collinearity of the variables.Results. Thirty-three patients (15 .7%) (31 men) developed ESRF. The five univariately significant variab les: gender, gross haematuria, 24-h proteinuria (24-P), serum creatini ne (SC), and antihypertensive treatment, were candidates for multivari ate analysis. The final model used SC (less than or equal to 100, 100- 150, >150 mu mol/l), 24-P (<1, greater than or equal to 1 g/day) and g ender (female Its male) as independent variables (relative risk and 95 % confidence interval were 3.5 (2.1, 5.9) for SC; 5.1 (1.9, 13.6) for 24-P; and 3.5 (0.9, 15) for gender). These estimates were used to cons truct a prognostic classification of ERSF for men with IgAN: stage 1 ( SC less than or equal to 150 mu mol/l and 24-P < 1 g/day), stage 2 ((S C > 150 mu mol/l and 24-P < 1 g/day) or (SC less than or equal to 150 mu mol/l and 24-P greater than or equal to 1 g/day)); stage 3 (SC > 15 0 mu mol/l and 24-P greater than or equal to 1 g/day). The ESRF-free s urvival was estimated with Kaplan-Meier analysis. It was 98.5% for sta ge 1, 86.6% for stage 2, 21.3% for stage 3 (P<0.001), 7 years after hi stological diagnosis. The validity of Lee's prognostic classification was confirmed using an independent sample. Conclusions. These classifi cations identify groups at high risk of ESRF. Therapeutic studies shou ld focus on these groups.