Cystatin C as a marker of renal function immediately after liver transplantation

To verify whether cystatin C may be of some use as a renal function marker immediately after orthotopic liver transplantation (OLT), we compared serum cystatin C (SCyst), serum creatinine (Scr), and creatinine clearance (Ccr) levels with the glomerular filtration rate (GFR). On postoperative days 1, 3, 5, and 7, SCyst and Scr was measured in simultaneously drawn blood samples, whereas Ccr was calculated using a complete 24-hour urine collection. The GFR was determined on the same days by means of iohexol plasma clearance (I-GFR). The correlation between 1/SCyst and I-GFR was stronger than that of 1/Scr or Ccr (P< 0.01). In the case of moderate reductions in I-GFR (80-60 mL/minute/1.73 m), Scr remained within the normal range, whereas the increase in Scyst was beyond its upper limit; for I-GFR reductions to lower levels (59-40 mL/minute/1.73 m), Scr increased slightly, whereas Scyst was twice its upper normal limit. When we isolated all of the I-GFR values on days 3, 5, and 7 that were >=30% lower than that recorded on the first postoperative day, SCyst(P< 0.0001) and Scr (P< 0.01) levels were increased, whereas Ccr remained unchanged (P= 0.09). Receiver operating characteristic (ROC) area-under-the-curve analysis showed that the diagnostic accuracy of Scyst was better than that of Scr and Ccr. Scyst levels of 1.4, 1.7, and 2.2 mg/L respectively predicted I-GFR levels of 80, 60, and 40 mL/minute/1.73 m. In conclusion, cystatin C is a reliable marker of renal function during the immediate post-OLT period, especially when the goal is to identify moderate changes in GFR. Liver Transpl 12:285-291, 2006. © 2006 AASLD.