A new serum cystatin C-based equation for assessing glomerular filtration rate in liver transplantation

Cystatin C (CysC) has been identified to be an alternative marker of glomerular filtration rate (GFR), but no CysC-based equation has been developed for patients receiving liver transplantation.

Serum CysC and (99m)Tc-DTPA clearance (true GFR) were measured simultaneously on post-transplant days 1, 4 and 7. A new equation was constructed based on an observation group of 30 patients and its predictive ability was compared with three other CysC-based equations (Hoek, Filler and Larsson) based on a validation group of 30 patients.

The new equation for calculating GFR was defined as 19.12+96.21x(1/CysC) and the derived GFR was estimated at 97.4+/-30.2 mL/min/1.73 m(2) and was close to the true GFR (96.8+/-32.8 mL/min/1.73 m(2)). Estimates of GFR by Hoek, Filler and Larsson formulas (61.4+/-25.4, 73.8+/-31.9 and 61.3+/-29.6mL/min/1.73 m(2), respectively) differed significantly from the true GFR. Correlation between the true GFR and all formulas showed no significant difference. Bias was neglectable for the new equation (mean difference: 0.6 mL/min/1.73 m(2)) but remarkable for the other three equations (mean difference: -22.9 to -35.4 mL/min/1.73 m(2)). Accuracy within 10%, 30% and 50% of the true GFR for the new equation (30.0%, 76.7% and 93.3%) was significantly higher than those of the other three equations (p<0.001 for all).

A new serum CysC-based equation was established in this study and it was shown to be accurate in estimating GFR after liver transplantation, compared to the formulas of Hoek, Filler and Larsson.