Background: Current estimates of renal function in kidney transplant patients are frequently inaccurate compared to radionuclide GFR (rGFR) measurement. Cimetidine inhibits tubular secretion of creatinine and improves the accuracy of formulas to estimate GFR.
Methods: We studied the effect of a cimetidine-aided (800 mg tid for 24 hr) serum creatinine on the correlation of creatinine clearance and three prediction formulas (Cockroft-Gault, Levey, and Nankivell) compared to rGFR in 15 kidney-pancreas transplant patients. Results were adjusted for body surface area.
Results: Correlations with rGFR using cimetidine-aided creatinine were: Cockroft-Gault, r=0.710; Levey, r=0.752; Nankivell, r=0.676; creatinine clearance, r=0.643. By Bland and Altman analysis, agreement with rGFR was best with the Nankivell and Cockroft-Gault equations and worst with creatinine clearance. Cimetidine ($0.48 Canadian) costs substantially less than the rGFR test ($66.00 Canadian).
Conclusion: Using cimetidine, prediction equations give a stronger correlation with GFR than creatinine clearance.