Different equations for estimating age-related changes of glomerular filtration rate in the healthy population

Identifying age-related trend of estimated glomerular filtration rate (eGFR) is necessary to assess whether kidney function is healthily aging. This study aimed to investigate the application of CKD-EPI, FAS, and Xiangya equations for the aging estimation of eGFR in the healthy Chinese individuals.

A total of 36,911 healthy individuals were enrolled in this study. We grouped every ten years to observe the trend of eGFR with aging and investigated decline rate of it by general linear regression analysis in each age-groups. Agreement between equations was determined by intraclass correlation coefficient (ICC) and Bland-Altman plot. We calculated reference interval in each age-group. We further analyzed above statistical indicators in males and females.

The eGFR by CKD-EPI, and Xiangya equation started to decline from the age of 18. Whereas eGFR by FAS equation remained stable under 40 years, then decreased more rapidly. Compared with males, the females had a higher level but a faster decline rate of eGFR with aging. Agreement analysis revealed good agreement between CKD-EPI and FAS equations (ICC 0.818-0.920). Agreement between Xiangya and CKD-EPI or FAS equations was poor to moderate in most of the population under 70 years old (ICC 0.282-0.786), but good in individuals above 70 years (ICC 0.769-0.881).

The trend of eGFR with aging was different by CKD-EPI, FAS, and Xiangya equations in the healthy Chinese. It may be necessary to take these equations- or age-related differences into consideration when assessing kidney function in primary health care and clinical practice.