Estimates of Glomerular Filtration Rate in Liver Transplant Recipients are not Accurate: A Role for 24-Hour Urine Creatinine Clearance

Background: Kidney injury is common among liver transplant recipients. Equations estimating glomerular filtration rate were not developed in liver transplant recipients. Aim: To determine if GFR equations and 24-hour urine creatinine clearance accurately estimate GFR in liver transplant recipients. Methods: 30 subjects were enrolled within 6 months of transplant and obtained estimates of GFR. The iothalamate scan served as the gold standard and it was compared to GFR equations and 24- hour urine creatinine clearance. Results: The mean time to iothalamate scan was 110 + 50 days.The mean iothalamate GFR was 90 + 37 mL/min/1.73 m2. The GFR equations underestimated GFR with 47%-63% of estimates differing by more than 20% from the iothalamate GFR. Among the equations the CKD-EPI-Cys-Cr was the most accurate. 24-hour urine creatinine clearance both under and overestimated GFR, however it was the most concordant with the iothalamate scan in identifying subjects with GFR greater or less than 50 mL/min/1.73 m2. Conclusions: Within 6 months of liver transplant GFR equations and 24-hour urine collection do not accurately estimate GFR. 24-hour urine creatinine clearance may be the clinically most useful estimate of GFR because it most accurately identifies liver transplant recipients with GFR greater or less than 50 mL/min/1.73 m2.