Cystatin C in acute kidney injury.

PURPOSE OF REVIEW: This review will summarize and discuss the role of cystatin C in the diagnosis of acute kidney injury.

RECENT FINDINGS: Cystatin C is easily measured and has the characteristics of an ideal marker of kidney function. Data suggest that cystatin C is modified by age, sex, muscle mass, obesity, smoking status, thyroid function, inflammation, and malignancy. These factors suggest the need for age-specific and sex-specific reference standards. Cystatin C-based glomerular filtration rate estimates may perform better than creatinine in selected patient populations (elderly, children, transplantation, cirrhosis, malnourished). Cystatin C has been evaluated for the early diagnosis of acute kidney injury (AKI) in several populations. Serum cystatin C has value for the diagnosis of acute kidney injury; however, it has often performed similarly to creatinine. Urinary cystatin C has potential as an early marker.

SUMMARY: Cystatin C is an accurate biomarker for the early detection of AKI, and may, in selected populations, be superior to creatinine; however, data have been inconsistent. It also has reasonable discrimination for important outcomes such as death and renal replacement therapy (RRT). Additional studies are needed that focus on the cost-effectiveness of earlier detection of AKI with cystatin C compared with creatinine, and whether these biomarkers have complementary value.