Application of the formula for estimating glomerular filtration rate in the elderly population

Objective To accurately assess the importance of glomerular filtration rate in the elderly population， explore the clinical characteristics of the elderly population who need to monitor glomerular filtration rate， and verify the performance of the currently commonly used estimated glomerular filtration rate （eGFR） formula.Methods A total of 313 patients aged 60 years and older who underwent ^99mTc-DTPA renal dynamic imaging for measured glomerular filtration rate （mGFR） in Tongji Hospital， Tongji Medical College， Huazhong University of Science and Technology from December 1， 2012 to December 31， 2021 were enrolled. The characteristics of elderly patients were analyzed. The consistency， precision and accuracy of commonly used eGFR formulas and mGFR were analyzed. Bland-Altman plots were used to compare the deviations between eGFR values calculated by each formula and mGFR values. The accuracy of each formula was evaluated by the proportion of eGFR within mGFR （1 ±10%） （P10）， the proportion within （1 ±30%） （P30）， mean percent error （MPE）， and mean absolute percent error （MAPE）. The deviations between the formulas were compared using the t-test， and the differences in P10 and P30 between the formulas were compared using the McNemar test.Results Results The age of the elderly population in this study was 68.3（63.0，72.0） years. All the commonly used eGFR formulas overestimated mGFR to varying degrees. The interquartile range （IQR）， MPE， MAPE， and root mean square error （RMSE） of the residual （eGFR-mGFR） were used to evaluate the accuracy of the formula eGFR. Both the Cockroft-Gault formula and the EKFC formula showed higher accuracy， among which the Cockroft-Gault formula had the lowest MPE and IQR， and the EKFC formula had the lowest MAPE and RMSE. The percentage of patients with absolute percentage errors within 10% and 30% was used as an indicator to evaluate the accuracy performance of the eGFR formula. Both the EKFC formula and the BIS1 formula showed higher accuracy， among which the EKFC formula had the highest P10 （26.8%）， and the BIS1 formula had the highest P30 （67.4%）. The C-MDRD formula performed the worst in both accuracy and precision.Conclusion All commonly used eGFR formulas overestimate mGFR in the elderly to varying degrees. In general， the EKFC formula has better performance in accuracy and precision， and the accuracy P30 of the EKFC formula is higher than that of the Cockroft-Gault formula， while the C-MDRD formula performs the worst in both accuracy and precision.