Background/Purpose:

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

Methods: An inception cohort of patients with biopsy proven ANCA-associated GN was studied retrospectively. Demographics, clinical, laboratory, serological and radiological parameters were analyzed. Patients were classified on the basis of renal histopathology, according to the report by Berden (1) et al into: focal class (≥50% normal glomeruli that were not affected by the disease process), crescentic class (≥50% of glomeruli with cellular crescents), sclerotic class (≥50% of glomeruli with global sclerosis), while all remaining biopsies were by definition not characterized by any of the predominant glomerular phenotypes and were classified as mixed class. Clinical phenotypes were assigned according to the second Chapel Hill vasculitides nomenclature Consensus Conference (2). A risk score was developed for each histopathological class using univariate and logistic regression analyses.

Results:

Of 147 eligible patients (136 from the University of Athens and 11 from the University of Ioannina), 105 had biopsy proven renal involvement. None of these patients had received any kind of immunosuppressive treatment at the time of kidney biopsy. Twenty out of the 105 pateints with renal involvement were excluded as they were younger than 16 years and had inadequate biopsy specimens (<10 glomeruli). Thus, the final study population consisted of 85 ANCA positive patients with biopsy proven GN.

Variables independently associated with focal class included disease duration up to diagnosis < 8 weeks, absence of red blood cell (RBC) casts by urine microscopy and eGFR > 49ml/min/1.73m²; with crescentic class > 40 erythrocytes/hpf, identification of RBC casts in urine, ear nose and throat (ENT) involvement and eGFR < 49ml/min/1.73m²; with mixed class age > 54 years, male gender, and absence of ENT involvement. In the presence of 2 or 3 risk factors a predictive risk score of each histopathological class was calculated: odds ratio (OR), 95% confidence intervals (CI), for focal class (≥2 risk factors) 17.5 (95% CI) [4.9-62.9], 38.0 [6.8-213.7] for crescentic class (≥3 risk factors), and 8.3 [1.0-67.5] (≥2 risk factors) for mixed class.

Conclusion: We propose a predictive algorithm of specific histolopathological classes of ANCA-associated GN, 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.

References:

1.Berden AE, Ferrario F, Hagen EC, Jayne DR, Jennette JC, Joh K, et al. Histopathologic classification of ANCA-associated glomerulonephritis. Journal of the American Society of Nephrology : 2010;21(10):1628-36.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/predictors-of-renal-histopathology-in-antineutrophil-cytoplasmic-antibody-associated-glomerulonephritis/