509-P: Utility of Serum Cystatin C in Early Kidney Dysfunction in Prediabetics

Background: Serum cystatin C (sCys C) has been proposed as a marker of kidney function with advantages compared to creatinine. It is unclear whether renal damage begin in prediabetes (PDM), when sCys C could be a promisor marker of early kidney dysfunction. We investigated whether sCys C differed between normoglycemic (NG) and PDM subjects and contributed to the detection of kidney dysfunction. Methods: A cross-sectional analysis of 947 nondiabetic participants (mean age 45.7 years) from the Brazilian Longitudinal Study of Adult Health was performed. sCys C (determined by ELISA) and CKD-EPI eGFR were compared between NG and PDM (fasting plasma glucose: 100-125 mg/dL or 2-hour post-load: 140-199 mg/dL or A1c: 5.7-6.4%). PDM were stratified in 4 groups according to altered sCys C and albumin excretion rate (AER): normal sCys C and AER (G1), abnormal sCys C and normal AER (G2), normal sCys C and abnormal AER (G3) and abnormal sCys C and AER (G4) were compared using ANOVA. Results: PDM subjects (n = 671) had anthropometric and biochemical data higher than NG (n=276), higher sCys C levels [0.67 (0.41-0.95) vs. 0.48 (0.31-0.81), p<0.001] and lower eGFR (96.3±17.4 vs. 100.6±17.1 mL/min/1.73m2, p<0.001). In eGFR categories (60-<90, 90-<125 and ≥125 mL/min/1.73m2), sCys C were always higher in PDM subjects than in NG. Comparing NG individuals, hyperfiltrants had lower sCys C than normofiltrants (p=0.03) but not than mildly reduced eGFR individuals (p=0.12). Considering the PDM groups, eGFR gradually dropped from G1 to G4 (96.8±17.4 vs. 96.2±16.9 vs. 94.0±17.2 vs. 77.2±25.4 mL/min/1.73m2, p-trend = 0.06) and, as expected, mean eGFR in G4 was lower than in G1 (p=0.017). Conclusion: Our data confirmed that sCys C is increased in PDM. Reduced sCys C only in NG hyperfiltrant subjects could suggest an inability of hyperfiltrant PDM to excrete Cys C. No statistical evidence that sCys C could be an early marker of kidney dysfunction in prediabetes was found; prospective studies should address its utility to detect dysfunction before AER elevation. Disclosure J.I.F. Branda: None. B. Almeida: None. S.R.G. Vivolo: None.