Validation and modification of renal risk score for prediction of long-term kidney survival in patients with MPO-ANCA-associated glomerulonephritis.

Background: Anti-neutrophil cytoplasmic antibody (ANCA) Renal Risk Score has not been widely validated in Chinese patients with myeloperoxidase -ANCA-associated glomerulonephritis and its predictive ability needs to be improved.

Methods: Three hundred and forty patients with biopsy-proven myeloperoxidase-ANCA-associated glomerulonephritis were included in this study. They were divided into an oliguric group (urine volume < 400 ml/24 h) and a non-oliguric group (urine volume ≥ 400 ml/24 h). The ANCA Renal Risk Score and Berden classes were used to predict the risk of end-stage kidney disease (ESKD), and Cox regression analysis was performed to evaluate the impact of oliguria on ESKD risk.

Results: The predictive performance of ANCA Renal Risk Score was significantly higher than that of Berden classes (AUC: 0.79 vs. 0.709, P = 0.003). Thirty-six (10.6%) patients presented with oliguria. Patients in the oliguric group had significantly lower levels of baseline estimated glomerular filtration rate (eGFR) [6.51(4.55-7.72) vs. 21.22(11.49-36.63) ml/min/1.73 m, P < 0.001], hemoglobin (78.33 ± 16.75 vs. 92.47 ± 18.95 g/L, P < 0.001), serum albumin (32.01 ± 5.92 vs. 36.22 ± 4.84 g/L, P < 0.001), and a lower percentage of normal glomeruli [6.86(0-17.39)% vs. 18.18(9.09-35)%, P < 0.001]. Consistently, the oliguric group had a higher percentage of patients that progressed to ESKD (83.3% vs. 36.2%, P < 0.001). Multivariate Cox regression analysis showed that oliguria was an independent risk factor for ESKD [HR = 2.38(1.39-4.06), P = 0.002]. Oliguria scores (3 points for presence and 0 for absence) were incorporated into the ANCA Renal Risk Score, resulting in ANCA Renal Risk Score-U. The patients were then categorized into four risk groups: low-(0-2 points), moderate-(3-7 points), high-(8-11 points) and very high-(12-14 points). The incidences of ESKD in these groups were 11.1%, 30%, 72.2% and 95.8%, respectively. The predictive efficacy of ANCA Renal Risk Score-U in predicting ESKD risk was significantly higher than that of the ANCA Renal Risk Score (AUC: 0.812 vs. 0.79, P = 0.025).

Conclusions: This study has validated the ANCA Renal Risk Score for predicting kidney outcomes among Chinese patients with myeloperoxidase-ANCA-associated glomerulonephritis. Furthermore, the ANCA Renal Risk Score-U model with oliguria as a variable can further improve the prediction of ESKD risk in patients with myeloperoxidase-ANCA-associated glomerulonephritis.