Serum Cystatin C as a Marker of Kidney Dysfunction in an Elderly Population

The prevalence of end-stage renal disease is increasing worldwide. Because nephropathy induced by type 2 diabetes accounts for most of the increase, a growing proportion of the patients are elderly. As preventive and renoprotective interventions are available, early identification of nephropathy is crucial, and there is a growing demand for a clinically convenient and reliable marker of renal function. Serum creatinine is widely used as a marker of the glomerular filtration rate (GFR), but the influence of muscle mass and, hence, the considerable interindividual variability limit its usefulness, especially in elderly individuals (1). Screening for microalbuminuria is used in assessing incipient nephropathy in diabetic patients, but the intraindividual variation and the need for repetitive urine sampling make it impractical in a geriatric setting. Serum cystatin C has been claimed to be a more sensitive indicator of GFR than serum creatinine (2)(3). It is unaffected by muscle mass, and it has been reported that cystatin C, unlike creatinine, might be able to mirror the involutional decrease in GFR that occurs with ageing (4)(5). Separate reference intervals for the elderly have been proposed in a few studies (5)(6)(7)(8), but the usefulness of cystatin C as a marker of renal function has not been extensively examined in large elderly populations. In a cross-sectional epidemiologic study, we compared serum cystatin C, serum creatinine, …