Study Recommends AAV Renal Risk Score to Predict Serious Kidney Disease in Patients

A combination of both blood tests and biopsy (tissue) analysis was better at predicting end-stage renal disease in people with anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV) compared to tissue analysis alone, a study has found. 

The scientists recommended using the AAV renal risk score (ARRS), which applies both clinical and biopsy (histopathology) findings, to best predict patient outcomes. 

The study, “Histopathological subgrouping versus renal risk score for the prediction of end-stage renal disease in ANCA-associated vasculitis,” was published in the Annals of the Rheumatic Diseases.

End-stage renal disease (ESRD) is a serious complication for people with AAV. Current predictors of AAV-related ESRD include age, kidney dysfunction, and findings from histopathology — the analysis and classification of diseased tissue under a microscope. 

Recently, ARRS was suggested as a more reliable predictor of ESRD. The score combines biopsy findings plus the glomerular filtration rate (GFR) — a measure of kidney function estimated from creatinine levels in the blood.

Thus, to assess whether ASSR is a better predictor for ESRD than tissue analysis alone, investigators based at the Izmir Katip Celebi University in Turkey reviewed the medical records, including biopsy findings, of 167 people with AAV to identify factors for renal disease survival.

Of those evaluated, 90 had the AAV subtype granulomatosis with polyangiitis, 39 with microscopic polyangiitis, 30 had renal-limited vasculitis, and eight were diagnosed with eosinophilic granulomatosis with polyangiitis. The median age at diagnosis was 55, and ANCA antibodies were detected in 87% of the 163 patients tested. 

All patients were treated with similar therapies starting with Cytoxan (cyclophosphamide) or the biological therapy Rituxan (rituximab) along with high doses of glucocorticoids during relapses. Maintenance therapy was a combination of methylprednisolone and azathioprine, Rituxan, or CellCept (mycophenolate mofetil) for at least two years after remission.

Over a median follow-up time of nearly 40 months, 52 patients (34%) developed ESRD and the median renal survival time — the time between diagnosis and ESRD — was 31 months. 

There were four groups of histopathology classification based on the extent of diseased tissue (from severe disease to low disease involvement) which included sclerotic (scarring), crescentic, mixed, and focal. 

Of the 106 kidney biopsies performed, histopathology found that 14 were sclerotic, 41 were crescentic, 33 were mixed, and 18 were focal. Of these, ESRD developed in 79% of those with sclerotic tissue, 51% in the crescentic group, 32% with mixed biopsy results, and 18% that were focal. 

According to the ARRS score, 14% were at low risk, 63% were at medium risk, and 23% were high risk for ESRD, and of those who developed ESRD, 8% were in the low-risk group, 42% in the medium-risk group, and 67% in the high-risk group.

A statistical analysis of the individual risk factors found that age at diagnosis, histopathology classification, creatinine levels, and GFR at baseline were significant. However, by combining all data together, ARRS itself was found to be an independent predictor for renal survival. 

“In conclusion, high ESRD development rates in AAV emphasizes the importance of identifying patients at risk,” the scientists said. 

“At this point, our results support the usage of both clinical and histopathological findings to predict the renal outcome.”