Cystatin C, Serum Creatinine, and Estimates of Kidney Function: Searching for Better Measures of Kidney Function and Cardiovascular Risk

Because kidney dysfunction is associated with adverse cardiovascular outcomes and death, clinicians are beginning to realize that accurately detecting even modest reductions in kidney function could help to identify patients who need extra attention.

Why is it important to identify early-stage kidney dysfunction accurately? Reduced kidney function is associated with increased incidence of cardiovascular morbidity and mortality in large cohorts of both selected and unselected patients (1, 2). This finding has led to the hypothesis that earlier recognition of kidney disease and successful intervention may improve outcomes of cardiovascular disease (CVD). No studies to date have determined the mechanism by which deteriorating kidney function worsens the prognosis of CVD. Moreover, no one knows whether strategies to delay the progression of chronic kidney disease actually improve the prognosis of CVD. The known associations of kidney dysfunction and inflammation and inflammation and CVD suggest that inflammation could be the link between kidney disease and CVD along with metabolic and hormonal abnormalities associated with chronic kidney disease (3).

Serum creatinine concentration is now recognized as an unreliable measure of kidney function because it is affected by age, weight, muscle mass, race, and various medications (4, 5). Several equations have been developed to improve the accuracy of serum creatinine level as a measure of glomerular filtration rate (GFR). The most widely used in adult populations are the Cockcroft–Gault (6) equation and the abbreviated Modification of Diet in Renal Disease equation (7). Even with these equations, measurement of GFR is difficult because the equations are less accurate at higher levels of kidney function and are affected by interlaboratory variation in measuring creatinine level.

Cystatin C concentration is a new and promising marker for kidney dysfunction in both native and transplanted kidneys (8-10). Cystatin …