Utility of cystatin C for assessment of renal function after cardiac surgery.

BACKGROUND: Though acute renal failure among cardiac surgery patients is associated with increased mortality, diagnosis of renal failure is often delayed due to the late detectability of laboratory markers for kidney failure. Recently, a number of clinical studies have shown that glomerular filtration rate (GFR) can be estimated by measuring the serum concentration of cystatin C (CysC). However, comparisons between the diagnostic effectiveness of CysC and serum creatinine have been inconsistent. The present study compares the diagnostic effectiveness of both serum markers in cardiac surgery patients.

METHODS: In 50 cardiac surgery patients, GFR was quantified by measuring creatinine clearance and estimated from serum concentrations of both creatinine and CysC. The sensitivity and specificity of serum creatinine and CysC for detection of reduced GFR values were compared as well as correlation between estimated GFR values and creatinine clearance.

RESULTS: GFR values <60 ml/min/1.73 m(2) were detected with equal effectiveness using creatinine or CysC, whereas for the detection of GFR <90 ml/min/1.73 m(2) the area under the curve of serum creatinine was significantly higher. Correlation between estimated GFR values and creatinine clearance was higher when creatinine-based formulae were used.

CONCLUSION: In patients after cardiac surgery, CysC is not superior to serum creatinine for assessment of GFR.