GFR Estimation Using a Panel of Filtration Markers in Shanghai and Beijing

Abstract Rationale and objectives Estimated GFR (eGFR) using creatinine and cystatin C may be less accurate compared to measured GFR (mGFR) in China than in North America, Europe and Australia due to variation across regions in their non-GFR determinants. The non-GFR determinants of beta-2 microglobulin (B2M) and beta-trace protein (BTP) differ from those of creatinine and cystatin C. Thus the average eGFR using all four markers (eGFRavg) could be more accurate than eGFR using creatinine and cystatin C (eGFRcr-cys) in China. Study design Diagnostic test study Setting and participants 1066 participants in Shanghai and Beijing with creatinine and cystatin C and 666 participants with all four filtration markers. Tests compared Index tests were previously developed equations for eGFR using creatinine, cystatin C, B2M and BTP and combinations. The reference test was mGFR using plasma clearance of iohexol. We compared the performance of eGFRavg to eGFRcr-cys using the proportion of participants with errors in eGFR greater than 30% of mGFR (1-P30) and root mean square error (RMSE) of the regression of eGFR on mGFR on the logarithmic scale. We also compared classification and reclassification of mGFR categories using eGFRavg compared to eGFRcr-cys. Outcomes Accuracy was significantly better for eGFRavg (1-P30 of 10.4% and RMSE of 0.214) compared to eGFRcr-cys (1-P30 of 13.8% and RMSE of 0.232; P=0.004 and P=0.006, respectively). However, improvements in accuracy did not generally translate into significant improvement in classification or reclassification of mGFR categories. Limitations Study population may not be generalizable to clinical settings other than large urban medical centers in China. Conclusions A panel of endogenous filtration markers including B2M and BTP in addition to creatinine and cystatin C may improve GFR estimation in China. Further study is necessary to determine whether GFR estimation using B2M and BTP can be improved and whether these improvements lead to useful clinical applications.