Cystatin C as a reliable marker of renal function following heart valve replacement surgery with cardiopulmonary bypass

Background: Little is known about serum cystatin C as a marker of renal function in cardiac surgery patients. The aim of this study was to assess its utility post cardiopulmonary bypass (CPB). Methods: 60 heart valve replacement patients were enrolled, and 26 of them had low-dose corticosteroid treatment on the first 3 days postoperatively. Serum creatinine, serum cystatin C and 24-h creatinine clearance rate (CCR) adjusted by body surface area were determined preoperation, days 1, 2, 3, 7 post operation. Results: Serum creatinine increased and peaked at day 3 postoperatively, while cystatin C peaked at day 2, and the adjusted CCR also reached a minimum at day 2. The inverse of cystatin C correlated better with CCR than that of creatinine (r=0.751 vs. 0.629). Using adjusted CCR as "golden standard", cystatin C was superior to creatinine in diagnosing renal dysfunction (area under the curve [AUC] for cystatin C 0.876, 95% confidence interval 81.8-93.4; AUC for creatinine 0.801, 95% confidence interval 72.5-87.7; p=0.045). Low-dose corticosteroid treatment has no significant effect on cystatin C. Conclusion: In agreement with many other investigators, the present findings support cystatin C is a reliable marker of renal function. It is superior to creatinine in patients post CPB. (c) 2006 Elsevier B.V. All rights reserved.