Prognostic Value of Microscopic Hematuria after Induction of Remission in Antineutrophil Cytoplasmic Antibodies-Associated Vasculitis.

Background: Pauci-immune glomerulonephritis (PIGN) is a major prognostic factor in antineutrophil cytoplasmic antibodies-associated vasculitis (AAV). Renal remission is usually defined as improvement or stabilization of serum creatinine and proteinuria levels but the significance of hematuria is unclear. We evaluated the prognostic value of microscopic hematuria in patients in remission from a first flare of PIGN. Methods: A multicenter retrospective study was conducted of all patients with histologically proven PIGN in northern France who presented a first renal flare of AAV between 2003 and 2013. All patients received conventional induction treatment and were considered in remission. Two groups were defined by the presence (H+) or absence (H-) of hematuria (dipstick 1+ and/or cytology 10,000 erythrocytes/mL). The primary outcome measure was the occurrence of renal relapse (RR) and/or end-stage renal disease (ESRD). Results: Eighty-six patients were included: 41 (48%) had hematuria at remission. The median follow-up time was 44 +/- 34 months. There was no significant difference between the groups in terms of the primary endpoint or the number of RR. However, the survival rate without RR was significantly lower in the H+ group (p = 0.002). In multivariate analysis, risk factors for RR were hematuria at remission for relapses within 44 months (hazard ratio [HR] 4.15; 95% CI 1.15-15.01; p = 0.03) and the duration of maintenance immunosuppressive therapy (HR 0.96 per additional month; 95% CI 0.94-0.99; p = 0.002). Conclusion: Hematuria at remission after a first PIGN flare was not associated with ESRD but with the occurrence of RR within 44 months of remission.