Comparison of Creatinine Clearance Estimates With Routine Measured Clearance in Adult Jordanians With a Kidney Transplant

OBJECTIVES: There are conflicting data on using the Cockroft-Gault formula and the Modification of Diet in Renal Disease formula to assess graft function in kidney transplants. This study uses a cohort of Jordanian kidney transplant patients to assess performance of the Cockroft-Gault formula and the Modification of Diet in Renal Disease equations by using the criterion standard of measured creatinine clearance. MATERIALS AND METHODS: Creatinine clearance measured by 24-hour urine creatinine in patients with a kidney transplant was compared with the estimated clearance using the Cockroft-Gault formula and the Modification of Diet in Renal Disease equations. Correlation, limits of agreement, and concordance analyses were used. RESULTS: There was a positive correlation between both the Cockcroft-Gault (r=0.878; P < .001) and the Modification of Diet in Renal Disease (r=0.732; P < .001) equations with creatinine clearance. The former was statistically superior (P = .0416). Using Bland-Altman plots, the limits of agreement were wide for both methods. After log transformation, the limits of agreement were -0.06 to +0.27 for the Cockcroft-Gault formula, and -0.21 to + 0.26 for the Modification of Diet in Renal Disease. Concordance analyses showed a correlation coefficient of 0.7384 (95% CI: 0.6134 to 0.8273) when the Cockcroft-Gault formula was used, and 0.7257 (95% CI: 0.5622 to 0.8345) for the Modification of Diet in Renal Disease. Pearson P coefficient (precision) and bias correction factor Cb (accuracy) for the Cockcroft-Gault formula and for the Modification of Diet in Renal Disease were 0.8762, 0.8427, 0.7324, and 0.9908. CONCLUSIONS: In Jordanian patients with a renal transplant, although the Cockcroft-Gault formula performed slightly better than the Modification of Diet in Renal Disease equation in estimating creatinine clearance, neither of these equations can accurately predict renal graft function.