Blood Test Identifies Individuals at Risk for Kidney Disease

The measurement of cystatin C levels in the blood has emerged as an alternative test of kidney function, because the protein is removed from the bloodstream by filtration in the kidneys.

Cystatin C levels rise in the blood when kidney function declines, while creatinine tests are inaccurate at detecting mild kidney impairment, and creatinine levels can vary with muscle mass and protein intake. In a study carried out at the San Francisco Veterans Affairs Medical Center, (San Francisco, CA, USA), 11,909 participants were investigated for various aspects of cardiovascular disease. The investigators defined CKD using both creatinine and cystatin C and compared their links to higher risks for premature death, cardiovascular events, heart failure, and kidney failure-all of which are known complications of CKD. Cystatin C was measured by means of a particle enhanced immunonephelometric assay (N Latex Cystatin C) with a nephelometer, both from Siemens Healthcare Diagnostics, (Deerfield, IL, USA).

In the group from a study of atherosclerosis (MESA), 9% of individuals had CKD by a creatinine-based equation only, 2% had CKD by a cystatin C-based equation only, and 4% had CKD by both equations. In the group from a cardiovascular health study (CHS), these percentages were 12%, 4%, and 13%, respectively. Compared with those without CKD, individuals in MESA with CKD based on creatinine only had similar risk of premature death, while individuals with CKD based on cystatin C only had more than a 3-fold increased risk, and those with CKD based on both had nearly a 2-fold increased risk.

The authors concluded that among adults diagnosed with CKD using the creatinine-based equation, poor prognosis is limited to patients who also have CKD according to the cystatin C-based equation. Therefore, cystatin C may have an important role in distinguishing the persons suspected of having CKD, based on the current creatinine definition, who have the highest risk for CKD complications. In addition, cystatin C may identify persons with high risk for CKD complications who are currently missed by creatinine. The study was published on December 16, 2010, in Journal of the American Society Nephrology.

Related Links:
San Francisco VA Medical Center
Siemens Healthcare Diagnostics