Is beta-trace protein an alternative marker of glomerular filtration rate in liver transplant recipients?

BACKGROUND: Renal insufficiency is common after liver transplantation (LT). The use of creatinine (Crea) as a marker of the glomerular filtration rate (GFR) is limited in patients after LT. Beta-trace protein (BTP), an alternative marker of GFR, is independent of muscle mass and has not been evaluated in LT recipients.

AIM: To evaluate BTP as an alternative tool to monitor renal function in LT recipients.

METHODS: We determined the diagnostic performance of BTP in comparison to Crea and cystatin C (CysC) in 52 patients, who concomitantly underwent (99m)Tc-DTPA-clearance measurements. Furthermore, we evaluated bias, precision and accuracy of five recently developed BTP-based equations to estimate GFR.

RESULTS: The average measured GFR was 51 (46.1; 56.0) ml/min/1.73 m(2). Using a cut-off of 30 ml/min/1.73 m(2) the area under the curve (AUC) was nearly identical for all markers. At a decision point of 60 ml/min/1.73 m(2) BTP showed only a trend towards a higher AUC compared with Crea and CysC (0.806 vs. 0.754 and 0.760, respectively; P>0.2). In comparison to the modification of diet in renal disease-formula (MDRD) only one of five BTP-based equations displayed a significantly higher accuracy within 30% of the measured GFR (84.6 vs. 59.6%; P=0.006). None of these equations showed a significant improvement compared with MDRD with respect to bias and precision.

CONCLUSIONS: Beta-trace protein can be used as an alternative diagnostic tool to detect moderate or severe GFR reduction in patients after LT. Furthermore BTP-based equations are able to estimate GFR in LT recipients. However, these equations fail to perform constantly better than the MDRD formula.