Predictors of renal histopathology in antineutrophil cytoplasmic antibody associated glomerulonephritis

Prompt, aggressive therapy is vital for anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis. In this regard, we aimed to identify predictors of distinct renal histopathological classes at the time of clinical diagnosis.

An inception cohort of patients with biopsy proven ANCA-associated glomerulonephritis was studied retrospectively. Demographics, clinical, laboratory, serological and radiological parameters were analyzed. Patients were classified on the basis of renal histopathology. A risk score was developed for each histopathological class using univariate and stepwise logistic regression analyses.

Variables independently associated with focal class included disease duration up to diagnosis <8 weeks, absence of erythrocyte casts by urine microscopy and eGFR >49 ml/min/1.73 m(2); with crescentic class >40 erythrocytes/hpf, identification of erythrocyte casts in urine, upper respiratory tract involvement and eGFR <49 ml/min/1.73 m(2); with mixed class age >54 years, male gender, and absence of upper respiratory tract involvement. In the presence of these risk factors a predictive risk score for each histopathological classes was calculated: odds ratio, 95% confidence intervals (CI), for focal class (≥2 risk factors, 20.8 (95% CI: 5.1-84.2), p < 0.0001, and 441.0 (95% CI: 16.8-11,590), p = 0.0003 for crescentic class (≥3 risk factors) while the small number of patients in the mixed and sclerotic class precluded any estimates.

We propose a predictive algorithm of specific histolopathological classes of ANCA-associated glomerulonephritis, which might provide a crude estimation of the disease activity in the glomeruli at presentation. This tool might assist the clinician in making decisions regarding the level of intensity of inductive immunosuppressive therapy at clinical diagnosis.