Clinical implications of using different methods for estimating kidney function in older hospitalised patients: creatinine, cystatin C, or both.

Cystatin C is an emerging alternative to creatinine for estimating kidney function. Formulae using cystatin C may more accurately reflect glomerular filtration rate than those based on creatinine. We prospectively evaluated the impact of formulae incorporating cystatin C for estimating the glomerular filtration rate (eGFR) in older inpatients. The eGFRs incorporating cystatin C predicted lower kidney function than predicted by creatinine, with more than 20% of patients receiving a new diagnosis of chronic kidney disease and possibly requiring drug dose adjustment.