SAT-407 OXFORD CLASSIFICATION AS A PREDICTOR OF RENAL PROGNOSIS IN IgA NEPHROPATHY PATIENTS AT THE NATIONAL KIDNEY AND TRANSPLANT INSTITUTE

Abstract

IgA nephropathy is one of the most common causes of glomerulonephropathy worldwide, with a higher incidence among those of Asian Pacific origin. Studies have shown that 10 to 30% of these patients reach end-stage renal disease (ESRD) within 10 years of diagnosis. It was also found that the rate of estimated glomerular filtration rate (eGFR) decline was significantly faster at 1.62 ml/min/1.72 m2 per year (31.7%) in this race, compared with other individuals of another race (24.8%). Markers of poor prognosis include the presence of hypertension, proteinuria and reduction in eGFR. Risk stratification is important in the management of IgA nephropathy to help physicians regarding renal prognosis and define goals of therapy. The Oxford classification was developed ito predict risk of disease progression. Key pathologic features that were found to be predictive of renal outcome were mesangial hypercellularity (M), endocapillary hypercellularity (E), segmental glomerulosclerosis (S) and tubular atrophy and interstitial fibrosis (T). Collectively, the MEST score has been validated across multiple populations predominantly in Europe, North America, Japan and China. It added value to prognostication however, the significant histopathologic lesion varied among different populations. Charts of 206 IgA nephropathy patients at the National Kidney and Transplant Institute from January 2010 to December 2017, who met the inclusion criteria, were reviewed. In comparison to previous international studies, our population were predominantly females (N = 116), with average age of 38.5 ± 11.2 years at time of biopsy and mean follow-up duration of 34.4 ± 22.9 months. Hypertension was present in 76 patients, predominantly in females (N = 42) as well. Mean eGFR was 68.5 ± 34.5 ml/min/1.73m² and mean proteinuria was 1.7 ± 1.8. Doubling of serum creatinine was observed in 29 patients who reached ESRD while reduction of eGFR >50% from baseline was seen in 31 patients of whom 25 needed renal replacement therapy (1 on peritoneal dialysis) and 6 had a kidney transplant (2 were pre-emptive). Baseline eGFR was 40.71 ± 19.6 at time of biopsy and 7.06 ± 4.03 on follow-up. Proteinuria was 2.6 ± 1.5 at time of biopsy and 6.3 ± 3.3 on follow-up. All histopathologic lesions were associated with higher amount of proteinuria. It was only the T score that was significantly associated with low eGFR. We tested the Oxford classification as a predictor of renal survival among 206 Filipinos with biopsy-proven IgA Nephropathy at the National Kidney and Transplant Institute, with a mean follow-up of 2.9 ± 1.9 years. We measured outcomes in terms of doubling of serum creatinine and >50% reduction of GFR from baseline. Our results showed that tubular atrophy/interstitial fibrosis was the most powerful histopathologic lesion to predict renal survival. Mesangial hypercellularity, endocapillary hypercellularity and segmental glomerulosclerosis showed no influence on renal survival, although they correlated with higher levels of proteinuria. Baseline renal function as well as tubular atrophy/interstitial fibrosis were strong independent variables in terms of >50% reduction of eGFR from baseline based on univariate analysis. This shows the significance of the Oxford classification in renal prognosis among different populations.