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

<jats:sec> <jats:title>Background and objectives</jats:title> <jats:p>The significance of persistent hematuria or proteinuria in patients with ANCA-associated vasculitis who are otherwise in clinical remission is unclear.</jats:p> </jats:sec> <jats:sec> <jats:title>Design, setting, participants, & measurements</jats:title> <jats:p>A <jats:italic toggle="yes">post hoc</jats:italic> 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.</jats:p> </jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>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; <jats:italic toggle="yes">P</jats:italic>=0.02); persistent proteinuria was not associated with renal relapse (subdistribution hazard ratio, 1.44; 95% confidence interval, 0.47 to 4.42; <jats:italic toggle="yes">P</jats:italic>=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; <jats:italic toggle="yes">P</jats:italic><0.01). The median time to renal relapse was 22 months.</jats:p> </jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>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.</jats:p> </jats:sec>