Elevated blood levels of the protein cystatin C accurately predict higher risk of chronic kidney disease, cardiovascular disease, and death among elderly people with no known kidney problems risks that the standard kidney function test, which measures the protein creatinine, misses entirely, according to a study led by a researcher at the San Francisco VA Medical Center.
"For the clinician who treats older people or others at risk for kidney disease, this is an important message: A normal creatinine level should not reassure you that your patient has normal kidney function," says lead author Michael Shlipak, MD, chief of general internal medicine at SFVAMC and an associate professor of medicine, epidemiology, and biostatistics at the University of California, San Francisco. "It shows that cystatin is a very promising new tool that complements creatinine in the ongoing effort to detect early kidney disease and prevent its complications."
The study appears in the August 15, 2006 issue of Annals of Internal Medicine.
Shlipak and his colleagues tested blood samples from 4,663 elders living independently in the community who participated in the Cardiovascular Health Study, a national longitudinal study of people aged 65 and older sponsored by the National Institutes of Health.
The researchers measured each participant's creatinine an end-product of muscle metabolism that is filtered through the kidneys and has been a standard marker of kidney health for "probably 100 years," according to Shlipak and cystatin C, a blood protein that is also filtered through the kidneys. They then matched test results with health outcomes up to nine years later.
Among participants with no diagnosed chronic kidney disease, those with high levels of cystatin C had significantly greater risk for poor health than those with normal cystatin C levels. Individuals in the high cystatin group were 50 percent more likely to die overall, nearly
Contact: Steve Tokar
University of California - San Francisco