Effect of malnutrition on serum creatinine and cystatin C levels

The concentration of cystatin C has been shown to be independent of age, gender and height, but the effect of malnutrition has not been studied. Levels of serum creatinine and cystatin C were estimated in 77 malnourished and 77 normally nourished boys between 2 years and 6 years of age without evidence of renal disease. The mean (95% confidence interval) serum creatinine level in the malnourished boys was significantly lower than that in the normally nourished boys [0.42 (0.38–0.45) mg/dl and 0.51 (0.48–0.55)] mg/dl, respectively, (P < 0.01)]. The mean level of serum cystatin C was 1.05 (0.94–1.17) mg/l and 1.12 (1.01–1.24) mg/l, respectively, in normally nourished and malnourished boys (P = 0.35). Mean glomerular filtration rate (GFR) estimated by the Schwartz equation in the malnourished boys was significantly higher than that in normally nourished children [141.8 (123.3–160.2) ml/min per 1.73 m² body surface area and 119.4 (109.3–129.5) ml/min per 1.73 m² body surface area], respectively (P = 0.04). However, the mean cystatin C-derived GFR was similar in the malnourished and normally nourished boys [99.70 (85.8–113.5) ml/min per 1.73 m² and 109.2 (94.4–124.0) ml/min per 1.73 m²], respectively (P = 0.35). The mean bias between GFR estimates using Bland and Altman analysis was greater in the malnourished children than in the normally nourished children (32.3% and 17.6%, respectively) (P = 0.15). Serum creatinine levels are lower in malnourished children and lead to overestimation of GFR, while cystatin C levels are unaffected.