A Novel Simpler Histological Classification for Renal Survival in IgA Nephropathy: A Retrospective Study

Background

Patients with immunoglobulin A (IgA) nephropathy may progress to end-stage renal disease (ESRD) within 10 to 20 years after renal biopsy. We evaluated factors associated with long-term renal survival by using a novel simplified histological classification.

Study Design

Retrospective study.

Setting & Participants

437 patients (296 men, 141 women) with IgA nephropathy seen at our single center from January 1971 to December 2006. Most patients received treatment with renin-angiotensin system inhibitors.

Predictors

Baseline age, sex, presence of hematuria, presence of hypertension, serum creatinine level, urine protein at baseline, and 2 histological classifications.

Outcomes & Measurements

Relationship of baseline factors to time to ESRD was evaluated by means of univariate and multivariate analysis with log-rank test and the Cox proportional hazard method.

Results

In a mean follow-up of 107.6 months, 72 ESRD events occurred. The 5-, 10-, 15-, and 20-year renal survival rates after renal biopsy were 94.1%, 82.1%, 73.1%, and 60.3%, respectively. Independent baseline predictors of increased ESRD risk were microhematuria with absence of recurrent macrohematuria (adjusted hazard ratio [HR], 2.18; 95% confidence interval [CI], 1.30 to 3.65; P = 0.003), 1.0 mg/dL (88.4 μmol/L) higher serum creatinine level (HR, 1.50; 95% CI, 1.10 to 2.07; P = 0.013), proteinuria with 1.0 g/dL (10.0 g/L) greater protein (HR, 1.28; 95% CI, 1.07 to 1.52; P = 0.006), and grading of histological lesions. A 1-grade increase according to our 3-grade classification was associated with a nearly 6-fold ESRD risk increase (adjusted HR, 5.95; 95% CI, 3.54 to 10.01; P < 0.0001).

Limitations

Lack of adjustment for changes in treatment that may have occurred during the study period.

Conclusions

Renal damage progression in patients with IgA nephropathy was associated with microscopic hematuria at clinical onset, increased serum creatinine level, increased proteinuria, and grading of histological lesions. Our classification system appears simpler than other classifications and is associated with ESRD risk, which could help identify individual high-risk patients and stratify patients enrolled in randomized clinical trials into homogeneous groups.

Index Words: Immunoglobulin A (IgA) nephropathy, histological classification, renal survival