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

Abstract

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.

Keywords: Anti-Neutrophil Cytoplasmic Antibody-Associated Vasculitis; Antibodies, Antineutrophil Cytoplasmic; Erythrocytes; Granulomatosis with Polyangiitis; Humans; Recurrence; Urinalysis; glomerulonephritis; hematuria; proteinuria; relapse; vasculitis.

Figure 1.

Persistent hematuria but not persistent proteinuria predicts a higher risk of renal relapse. Cumulative incidence curves for renal relapse in patients with and without (A) persistent hematuria for 6 months, and (B) persistent proteinuria for 6 months. Adjusted for study: ANCA type (antiproteinase 3 versus antimyeloperoxidase), pulmonary involvement, and baseline creatinine. Relapse without renal involvement and development of ESRD were competing events.