Abstract
BackgroundClinical and pathologic features that predict outcome have important potential application in patients with pauci-immune necrotizing glomerulonephritis (usually antineutrophil cytoplasmic antibody–associated vasculitis). This study examines the predictive value of simple quantitative renal histologic measurements in a large cohort with extended follow-up.Study DesignCohort study.Setting & Participants390 consecutive patients with pauci-immune necrotizing glomerulonephritis at a single hospital (1983-2002); 90 patients underwent repeated kidney biopsy during follow-up.PredictorsAge and serum creatinine concentration at biopsy, antineutrophil cytoplasmic antibody specificity, percentage of normal glomeruli, percentage of glomeruli with active lesions, and index of chronic damage (quantitative measurement of established cortical damage) in the initial kidney biopsy for all patients. The same factors were assessed in both biopsy specimens for patients undergoing an additional biopsy.Outcomes & MeasurementsEnd-stage renal disease and patient survival.ResultsMortality at 1 and 5 years was 23% and 40%, respectively: standardized mortality ratio, 4.74 (95% CI, 3.62-6.32). End-stage renal disease was reached by 14% and 18% at 1 and 5 years, respectively. In multivariable analysis, serum creatinine level at biopsy and percentage of normal glomeruli in the initial biopsy specimen were the best predictors of kidney survival. C Statistics were 0.80 for creatinine level alone and 0.83 for creatinine level with normal glomeruli. In patients undergoing an additional biopsy, rapid progression in the index of chronic damage and serum creatinine level at the second biopsy were associated with kidney survival in multivariable analysis.LimitationsRetrospective analysis. External validity of the index of chronic damage requires further assessment. Selection bias may influence repeated biopsy analyses.ConclusionsSerum creatinine level at biopsy best predicts kidney survival in patients with pauci-immune necrotizing glomerulonephritis overall.
Highlights
Clinical and pathologic features that predict outcome have important potential application in patients with pauci-immune necrotizing glomerulonephritis
End-stage renal disease was reached by 14% and 18% at 1 and 5 years, respectively
Serum creatinine level at biopsy and percentage of normal glomeruli in the initial biopsy specimen were the best predictors of kidney survival
Summary
Clinical DataAll patients at the Queen Elizabeth Hospital, Birmingham, UK, with a diagnosis of pauciimmune necrotizing glomerulonephritis by kidney biopsy between 1983 and 2002 were included. Clinical data were obtained from patient records (hospital and general practice). Serum creatinine was measured at the time of biopsy or before the initiation of acute dialysis therapy if this occurred before the biopsy was performed. Biopsies ordinarily were performed before administration of immunosuppressive therapy or shortly thereafter in exceptional cases. Repeated biopsies ordinarily were performed before escalation of immunosuppression. Patients were defined as reaching the end point of end-stage renal disease (ESRD) when they required permanent renal replacement therapy, in other words, long-term dialysis therapy or transplant. Patients who required acute dialysis at presentation or relapse, but who recovered independent kidney function after treatment, were not classified as reaching the end point. Time to the end point was defined as time elapsed between biopsy (time zero) and either death or initiation of permanent renal replacement therapy. Research was conducted in accordance with the Declaration of Helsinki
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