Implications of using Cockcroft-Gault and Modification of Diet in Renal Disease Study equations to estimate renal function in ethnic Korean patients

Purpose. Variations in renal function calculations performed with different estimating equations were investigated using data on a large nationally representative sample of Korean adults. Methods. A retrospective, cross-sectional, population-based analysis was conducted using 2007-09 data from the Korea National Health and Nutrition Examination Survey. Estimated creatinine clearance (CI_cr) values for the study sample (n = 16,002) were calculated using the Cockcroft-Gault (CG) formula, and glomerular filtration rate estimates were performed using the four-variable Modification of Diet in Renal Disease (MDRD) Study equation, with normalization of values for body surface area. Renal function estimates derived from the CG and MDRD equations were compared among subgroups; rates of disagreement in the categorization of subjects for medication dose adjustments according to widely used CI_crcutoff values were analyzed. Results. In the study sample as a whole and all evaluated subgroups, renal function estimates performed via the CG and MDRD equations differed significantly (p < 0.001); the greatest differences were seen in calculated values for the elderly, patients with diabetes, and those with a body mass index of ≥25 kg/m²or a serum creatinine concentration of <1 mg/dL. Maximum rates of disagreement in dosage-adjustment categorizations by the CG and MDRD equations were observed at the highest CL_crcutoff values and ranged from 6.7% to nearly 20%. Conclusion. The study revealed disagreements in renal function estimates performed using CG and MDRD equations in a large sample of ethnic Korean adults, with more pronounced differences observed in certain subgroups.