Comparison of bias and accuracy using cystatin C and creatinine in CKD-EPI equations for GFR estimation

Background: The directly measured glomerular filtrate rate (mGFR) is the gold standard for kidney function, but it is invasive and costly. The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations have been widely used to estimate GFR, however, the comparative accuracy of estimated GFR (eGFR) using creatinine and cystatin C in CKD-EPI equations remains unclear. We performed this meta-analysis to assess the bias and accuracy of eGFR using equations of CKD-EPIcrea, CKD-EPIcys and CKD-EPIcrea/cys, in adult populations relevant to primary health care. Methods: Pubmed, Web of Science, EMBASE, and the Cochrane Library were searched from inception until December 2019 for related studies. Results: A total of 35 studies with 23,667 participants, which reported the data on the bias, and/or P30, and/ or R were included. The difference in the bias of eGFR using CKD-EPIcys was 4.84 mL/min/1.73 m(2) (95% CI, 1.88 similar to 7.80) lower than using CKD-EPIcrea, and 1.50 mL/min/1.73 m(2) (95% CI, 0.05-2.95) lower than using CKD-EPIcrea/cys. These gaps increased in subgroups of low mGFR (<60 mL/min/1.73 m(2)). CKD-EPIcrea/cys eGFR achieved the highest accuracy, 7.50% higher than CKD-EPIcrea (95% CI, 4.81-10.18), and 3.21% higher than CKD-EPIcys (95% CI, -0.43 similar to 6.85); and the best correlation with mGFR, with Fisher's z transformed R of 1.20 (95% CI, 0.89-1.50). Conclusions: CKD-EPI(crea/cys )and CKD-EPIcys gave less bias and more accurate estimates of mGFR than CKD-EPIcrea. More variables and coefficients could be added in CKD-EPI equations to achieve less bias and more accuracy in future research.