Histopathological classification of antineutrophil cytoplasmic antibody-associated glomerulonephritis: an update

This review discusses the findings of studies validating the histopathological classification of antineutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis, which was devised in 2010 by an international working group of pathologists and nephrologists in collaboration with the European Vasculitis Society.

So far, eight studies have validated the histopathological classification of ANCA-associated glomerulonephritis. The studies came from Japan, China, Australia, the United States, the Netherlands, and Turkey. These validation studies confirmed that the histopathological classification of ANCA-associated glomerulonephritis is of predictive value for renal outcome. This was especially the case for patients with either a focal or sclerotic-class renal biopsy, whereas the crescentic and mixed classes showed different results in the validation studies. These differences could be due to differences in patient populations or therapy, inter-rater reliability and lack of inclusion of tubulointerstitial lesions in the classification. Therapy is known to influence renal outcome, but due to the retrospective design of the to-date performed validation studies, this parameter could not be fully accounted for in these validation studies. Inter-rater reliability among three histopathologists was investigated in one study and was moderate.

The histopathological classification of ANCA-associated glomerulonephritis predicts renal outcome during follow-up, especially in patients with a focal or sclerotic-class renal biopsy. A large international validation study is currently being performed.

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