Predicting renal outcome in antineutrophil cytoplasmic antibody (ANCA)-associated
glomerulonephritis (GN) remains a major challenge. We aimed to identify reliable predictors
of end-stage renal disease (ESRD) and to develop and validate a clinicopathologic
score to predict renal outcome in ANCA-associated GN. In a prospective training cohort
of 115 patients, the percentage of normal glomeruli (without scarring, crescents,
or necrosis within the tuft) was the strongest independent predictor of death-censored
ESRD. Regression tree analysis identified predictive cutoff values for three parameters:
percentage normal glomeruli (N0 >25%, N1 10 to 25%, N2 <10%), percentage tubular atrophy
and interstitial fibrosis (T0 ≤25%, T1 >25%), and estimated glomerular filtration
rate at the time of diagnosis (G0 >15 ml/min/1.73 m2, G1 ≤15 ml/min/1.73 m2). Cox
regression analysis was used to assign points to each parameter (N1 = 4, N2 = 6, T1 =
2, G1 = 3 points), and the resulting risk score was used to classify predicted ESRD
risk as low (0), intermediate (2 to 7), or high (8 to 11 points). The risk score accurately
predicted ESRD at 36 months in the training cohort (0%, 26%, and 68%, respectively)
and in an independent validation cohort of 90 patients (0%, 27%, and 78%, respectively).
Here, we propose a clinically applicable renal risk score for ANCA-associated GN that
highlights the importance of unaffected glomeruli as a predictor of renal outcome
and allows early risk prediction of ESRD.