P0113STANDARDIZED GRADING OF CHRONIC CHANGES IN MINIMAL CHANGE DISEASE: A VALIDATION STUDY IN NATIVE KIDNEY BIOPSY SPECIMENS

Abstract

Abstract Background and Aims Recently, a group of pathologists and nephrologists devised a simple scoring system for chronic changes based on the grading of glomerulosclerosis (GS), tubular atrophy (TA), interstitial fibrosis (IF) and arteriosclerosis (AS). We aimed to validate for the first time this score in patients with minimal change disease. Method We included 79 adult patients (age 50.3 (46.3, 54.3) years, 57% male, eGFR 54.7 (44.2, 63.5) mL/min) with biopsy proven MCD between 2010-2015 who were followed up until January 1, 2017. The extent of GS, TA and AS was scored from 0 to 3, 0 to 3 and 0 to 1, respectively. The scores were then added (total renal chronicity score) to grade the overall severity of the chronic lesions into minimal (0–1 total score), mild (2–4 total score), moderate (5–7 total score) and severe (>8 total score). The outcomes were: patient survival; kidney survival defined as doubling of serum creatinine or ESRD; partial (proteinuria 0.3 to 3.5g/24h) or complete remission (proteinuria <0.3g/24h) - whichever came first. Variables related to renal outcome were further evaluated in a multivariate Cox proportional hazard (CPH) model. Results Minimal chronic lesions were found in 77%, mild in 18% and moderate in 5% of the studied patients. Fifty percent had a null score of chronicity; they were younger (44 (29-53) versus 62 (44-66) years, p<0.001), had higher eGFR (65.0 (42.1-83.2) versus 43.4 (25.8-63.9) mL/min, p<0.01) but similar proteinuria (4.8 (1.9-8.2) versus 4.5 (1.1-6.7) g/g, p=0.3). Patients with a score higher than one had higher mortality (18% versus 0%, p<0.001) and started RRT more often (15% versus 0%, p=0.01). There were no differences regarding the presentation as acute kidney injury, and in reaching complete or partial remission. Moreover, there were no clinical or pathology features that predicted remission. 17% of the patients reached the composite endpoint of kidney survival; mean kidney survival time was 5.7 (5.2, 6.3) years. In the CPH analysis the only independent predictors of decreased renal survival were elevated chronicity score (HR 1.56 (95%CI 1.14-2.14), p<0.01), lower serum albumin (HR 0.27 (95%CI 0.08-0.88), p=0.03) and the presence of hypertension (HR 0.18 (95%CI 0.03-0.93), p=0.04). Conclusion To the best of our knowledge, this is the first study to validate the standardized grading of chronic changes as an independent predictor of renal survival in patients with minimal change disease.