The validation of the EKFC equation for Glomerular Filtration Rate estimation and comparison with the Asian Modified CKD-EPI equation in Chinese Chronic Kidney Disease patients in the external study

Abstract Objective To verify whether a Modified Full Age Spectrum Creatinine-Based Equation (EKFC equation) is more applicable than the Asian Modified CKD-EPI equation in the clinical practice, which was confirmed with higher accuracy in estimating Glomerular Filtration Rate (GFR) in our external Chronic Kidney Disease (CKD) populations.Methods According to the EKFC equation and the Asian Modified CKD-EPI formula, we calculated estimated GFREKFC and GFRCKD-EPI, separately. Clinical diagnostic performance of the two equations was assessed and compared by correlation coefficient, regression equation, Bland–Altman analysis, bias, precision, accuracy(P30) and the incorrectly reclassified index under the premise of 99mTc-diethylenetriaminepentaacetic acid (99mTc-DTPA) dual plasma sample clearance method as reference method for GFR measurement (mGFR).Results Totally, 160 CKD patients were recruited in our external cohort. The GFREKFC was highly related with mGFR, with the correlation coefficient of 0.95 [95%CI, 0.93-0.96], (P<0.01) and regression equation of GFREKFC= mGFR*0.87+5.27. Compared with the Asian Modified CKD-EPI equation, the EKFC equation demonstrated a wider bias（-1.64 vs 0.84 ml/min/1.73 m2, P<0.01）, nearly identical precision (12.69 vs 12.72 ml/min/1.73 m2, P=0.42) and P30 (80.0% vs 74.4%, P=0.57). Furthermore, the 95% limit of agreement in Bland-Altman analysis of the two target equations were almost same (42.4 vs 44.4 ml/min/1.73 m2). And, the incorrectly reclassified index among the different CKD stages between the two models was not statistically different.In the mGFR≤60 ml/min/1.73 m2 subgroup analysis, the precision of the EKFC equation was better than the Asian Modified CKD-EPI formula (9.78 vs 10.25 ml/min/1.73 m2, P<0.01), and the bias and P30 were not statistically different. However, in the mGFR>60 ml/min/1.73 m2 subgroup, the EKFC equation did not performed better than the Asian Modified CKD-EPI formula with a wider bias (-8.60 vs -0.42 ml/min/1.73 m2, P<0.01), an inferior precision (16.39 vs 15.86 ml/min/1.73 m2, P<0.01), and a statistically invalid P30 (95.7% vs 94.2%, P=1.00).Conclusion The total performance of the EKFC equation is acceptable. However, compared with the Asian Modified CKD-EPI equation, the EKFC equation is not more accurate to estimate GFR in our external Chronic Kidney Disease populations.