Abstract
Background: 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.
Methods: Serum CysC and 99mTc-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.
Results: The new equation for calculating GFR was defined as 19.12+96.21×(1/CysC) and the derived GFR was estimated at 97.4±30.2 mL/min/1.73 m2 and was close to the true GFR (96.8±32.8 mL/min/1.73 m2). 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 m2, 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 m2) but remarkable for the other three equations (mean difference: −22.9 to −35.4 mL/min/1.73 m2). 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).
Conclusions: 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.
Clin Chem Lab Med 2008;46:405–10.
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