Microscopic Haematuria in ANCA-Associated Vasculitis with Glomerulonephritis During Treatment and Remission

Background: ANCA-associated small vessel vasculitides (AAV) are prone to cycles of relapse and remission. Renal involvement manifests as glomerulonephritis with microscopic haematuria, red blood cell casts, proteinuria and variable decrease in renal function. Remission of renal vasculitis is defined as stabilization in serum creatinine (Creat) and resolution of haematuria while controversy exists about persistence of haematuria (during apparent disease-remission) since it may indicate smouldering disease-activity or should be considered as renal flare. Objective: To clarify the course of haematuria after diagnosis and induction therapy and its possible predictive value of long term renal function. Design: Retrospective cohort study. Participants: 96 consecutive AAV-patients with renal involvement diagnosed and treated with systemic AAV between 1st of January 2000 to 31th December 2007 were followed for 60 months. Main measures: Collected data were Creat, CRP (mg/ml), eGFR ml/min/1.73 m2, creatinine-excretion in collected 24 h urine (Ucreat/24 h), proteinuria (Uprot), ratio of proteinuria/ creatinine in 24 h urine (Uprot/creat) and haematuria. Data were analysed for the complete study population and compared for MPO-ANCA and PR3-ANCA. Key results: At twelve months after diagnosis, haematuria was no longer detectable in 92% of all patients. In the PR3-ANCA group, haematuria disappeared after 13 months, while in the MPO-ANCA group haematuria persisted in 19% of the patients. On average, haematuria disappeared almost simultaneously with stabilisation of the renal function. Conclusion: Haematuria persists for many months after diagnosis and disappears usually simultaneously with stabilisation of kidney function. There was no relation between persistence of haematuria for over 12 months and renal function during follow up. Haematuria probably acts as a sensitive marker for absence of inflammatory glomerular disease activity in most patients with systemic AAV and renal involvement. It is disappearance coincide with stabilisation of renal function and remission of the disease in almost all patients. However, if it persists, it is not predictive for worsening renal function nor for relapse. Proteinuria does not seem to be a reliable marker for renal disease remission