Performance of MDRD-IDMS and CKD-EPI equations in Mexican individuals with normal renal function.

Background:  The performance of the CKD-EPI and MDRD formulae for estimating glomerular filtration rate (GFR) in patients of Hispanic origin with normal renal function has been poorly explored and requires validation in Mexico. 
Material and Method:  We included previously healthy Mexican adults. We obtained clinical variables and determined serum creatinine to calculate the CKD-EPI and MDRD-IDMS formulae. These results were compared with the gold standard (GFR measured by Tc99DTPA). We evaluated other clinical variables that could affect the performance of the CKD-EPI formula. 
Results:  A total of 97 healthy volunteers were included, 55 males and 42 females; the mean age was 35.8 years old (18 to 73). Mean creatinine was 0.76mg/dl (±0.18). CKD-EPI performance was significantly better than MDRD-IDMS in all comparisons (bias, correlation and accuracy). The bias difference between the formulae was 6.08ml/min/1.73m2 (95% CI 2.58 to 9.58) (p<.001). Individuals with a body mass index (BMI) above 25kg/m2 displayed a better performance than the group with a lower BMI (difference of means 7.39ml/min/1.73m2; 95% CI 1.17 to 13.6 p<.02). Both formulae overestimated the GFR. BMI was significantly associated with the performance of the CKD-EPI formula (β 0.82; 95% CI 0.085 to 1.56 p=.029). 
Conclusions:  In healthy Mexican adults, the CKD-EPI formula is a better predictor of the mGFR than the MDRD-IDMS formula. BMI is significantly associated with the performance of the CKD-EPI formula and is better in those with a BMI greater than 25kg/m2. Both formulae overestimate mGFR.