The Xiangya equation could not replace the Asian modified CKD-EPI equation in estimating glomerular filtration rate in Chinese patients with chronic kidney disease

Background To evaluate the clinical practicability of the Xiangya equation in estimating glomerular filtration rate (GFR) and compare with the Asian modified Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) equation, assessing whether the Xiangya equation could replace the Asian modified CKD-EPI equation as the preferred method for predicting GFR in the Chinese CKD patients in an external validation study. Methods The GFR was determined simultaneously by two methods: (a) the Asian modified CKD-EPI equation (GFR(CKD-EPI)); (b) the Xiangya equation (GFR(Xiangya)); diagnostic performance of the two models was compared by the regression analysis, the Bland-Altman plot, bias, precision and P-30 under the background of Tc-99m-diethylenetriaminepentaacetic acid (Tc-99m-DTPA) dual plasma sample clearance method as reference method for GFR measurement (mGFR). Results A total of 158 Chinese CKD patients were included in our external study. The GFR(Xiangya) was highly related with mGFR, with the correlation coefficient of 0.92. The regression equation was GFR(Xiangya) = 0.55*mGFR + 28.25, where the regression coefficient was far away from one and the intercept was wide. Compared with the Asian modified CKD-EPI equation, the performance of the Xiangya equation demonstrated a poorer bias (9.5 vs - 3.3 ml/min/1.73 m(2), P < 0.001), an inferior precision (23.9 vs 13.0 ml/min/1.73 m(2), P < 0.001), a lower P-30 (51.3% vs 73.4%, P < 0.001) and a wider 95% limit of agreement in Bland-Altman analysis (65.0 vs 44.9 ml/min/1.73 m(2)). Conclusion Due to relatively inferior performance, the Xiangya equation could not replace the Asian modified CKD-EPI equation in estimating GFR in Chinese patients with chronic kidney disease in our external cohort.