Evaluation of six GFR estimation equations in Chinese patients with chronic kidney disease.

BACKGROUND

Glomerular filtration rate (GFR) is recognized as the most reliable indicator of renal function and is usually estimated based on the serum creatinine equations. However, the reliability of these equations in specific regions needs to be properly quantified. We evaluated the applicability of the abbreviated MDRD equation (aGFR), the modified abbreviated MDRD equation (maGFR), the CKD-EPI creatinine equation (C-GFRcr), the CKD-EPI creatinine-cystatin C equation (C-GFRcr-cys), the EKFC creatinine equation (E-GFRcr), and the EKFC creatinine-cystatin C equation (E-GFRcr-cys) to chronic kidney disease (CKD) patients in Chongqing, China.

METHODS

A total of 234 adult patients with CKD were selected for the study. Their sex, age, and etiology of CKD were recorded, and serum creatinine and cystatin C were measured and traceable to primary reference materials. The technetium 99 m-labeled diethylenetriamine pentaacetate (99mTc-DTPA) renal scintigraphy was used as the reference method for GFR measurement. Six GFR estimation equations were analyzed in the overall analysis and across various stages of CKD to evaluate differences, absolute differences, bias, precision, and accuracy.

RESULTS

In the validation dataset, the differences for maGFR were smaller compared to other equations, while those for C-GFRcr-cys and E-GFRcr-cys were larger. The bias for C-GFRcr-cys and E-GFRcr-cys was significantly higher than that of the other equations, although all six equations exhibited similar levels of precision. In CKD stages 1 through 3, the accuracy of C-GFRcr-cys and E-GFRcr-cys was significantly lower when compared to the other equations. Conversely, in CKD stages 4 and 5, maGFR and E-GFRcr-cys demonstrated significantly greater accuracy than the other equations. In CKD stage 1, maGFR misclassified only 5.21 % of patients, whereas C-GFRcr-cys and E-GFRcr-cys had significantly higher misclassification rates of 66.67 % and 68.75 %, respectively, compared to the other equations.

CONCLUSIONS

Overall, maGFR performed better than other equations and can be used as a confirmatory test in CKD patients in Chongqing, China.