The Utility of Urinalysis in Determining the Risk of Renal Relapse in ANCA-Associated Vasculitis.

Background and Objectives: The significance of persistent hematuria or proteinuria in patients with ANCA-associated vasculitis who are otherwise in clinical remission is unclear.
Design, Setting, Participants, & Measurements: A post hoc analysis was conducted using participants enrolled in two randomized, placebo-controlled clinical trials who had active GN due to ANCA-associated vasculitis, had positive ANCA, and achieved remission by month 6. Dipstick and microscopic urinalyses were performed at each visit. Persistent hematuria or proteinuria for at least 6 months and the cumulative duration of hematuria were examined. Renal relapse was defined as new or worsening red blood cell casts and/or worsening kidney function according to the Birmingham Vasculitis Activity Score for Granulomatosis with Polyangiitis.
Results: There were 149 patients included in this study: 42% had persistent hematuria, and 43% had persistent proteinuria beyond 6 months. Persistent hematuria was associated with a significantly higher risk of relapse, even after adjusting for potential confounders (subdistribution hazard ratio, 3.99; 95% confidence interval, 1.20 to 13.25; P =0.02); persistent proteinuria was not associated with renal relapse (subdistribution hazard ratio, 1.44; 95% confidence interval, 0.47 to 4.42; P =0.53). Furthermore, greater cumulative duration of hematuria was significantly associated with a higher risk of renal relapse (adjusted subdistribution hazard ratio, 1.08 per each month; 95% confidence interval, 1.03 to 1.12; P <0.01). The median time to renal relapse was 22 months.
Conclusions: In patients with ANCA-associated vasculitis and kidney involvement who achieve remission after induction therapy, the presence of persistent hematuria, but not proteinuria, is a significant predictor of future renal relapse.
(Copyright © 2018 by the American Society of Nephrology.)