Serum cystatin C as a better marker of vancomycin clearance than serum creatinine in elderly patients

Objectives:The purpose of this study is to assess the usefulness of the concentration of cystatin C (Cys-C) in serum for predicting the clearance of vancomycin (CLvcm) compared with the serum concentration of creatinine (SCr) in the elderly.Methods:Thirty-nine serum samples were obtained from 24 elderly patients (65 years and older). Creatinine clearance (CLcr) and the glomerular filtration rate calculated from the concentration of Cys-C (GFRcys-c) were estimated using Cockcroft & Gault's formula and Larsson's formula, respectively.Results:The correlation constant for CLvcm and the reciprocal of Cys-C (p = 0.883) was significantly higher than that for CLvcm and the reciprocal of SCr (p = 0.575, p < 0.005). GFRcys-c was strongly correlated with CLvcm (p = 0.883) and the constant was significantly higher than that for the correlation between CLvcm and CLcr (p = 0.684, p < 0.05). These results suggest that the serum concentration of Cys-C is a more reliable marker for predicting CLvcm than is SCr in elderly patients.