Cystatin C is a protein produced by nearly all human cells and excreted into the bloodstream. As a serum measure of renal function, it appears to be independent of age, sex and lean muscle mass. This study compares the associations of cystatin C, creatinine and the glomerular filtration rate (GFR) to ascertain which measure is a stronger predictor of illness and death in an elderly population sample. Data were obtained from the Cardiovascular Health Study of which the main purpose was to evaluate risk factors for the development and progression of cardiovascular disease in elderly persons. Serum samples were collected from 4,637 participants in 1992 and 1993 and follow-up continued until 2001.
The key findings were:
- Higher cystatin C levels were directly associated with a higher risk of death from all causes.
- Higher cystatin C levels were directly associated with an elevated risk of death from cardiovascular causes, myocardial infarction and stroke.
- Only the highest creatinine subgroup had an increased risk of death and only the lowest estimated GFR levels.
The study showed that cystatin C provides a stronger estimate of the risk of cardiovascular events and death among elderly persons than either the creatinine level or the estimated GFR. A future study would be to determine whether cystatin C has value in clinical medicine as an improved measure of renal function in elderly patients.