Comparison of glomerular filtration rate estimating formulas among Japanese adults without kidney disease

Previous studies have proposed different formulas of estimating glomerular filtration rate (eGFR) among clinical patients. The comprehensive comparison of eGFR formulas is not well established in a Japanese population. We compared eGFR values and chronic kidney disease (CKD) classification of nine different eGFR in a Japanese general population sample.

We analyzed 469 Japanese community-dwelling adults (184 men) without any self-reported kidney disease. GFR estimated using the 4- and 6-parameter Modification of Diet in Renal Disease (MDRD) formulas (MDRD4 and MDRD6); the CKD-EPI formulas based on creatinine with (CKD-EPI-2009) and without race coefficient (CKD-EPI-2021), on cystatin C (CKD-EPI-Cys), on both (CKD-EPI-CreCys); the Japanese creatinine-based formula (JPN-Cre), cystatin C-based formula (JPN-Cys), and modified CKD-EPI formula (JPN-CKD-EPI). CKD stages were defined by KDIGO guidelines (eGFR < 60 ml/min/1.73 m²).

eGFR_JPN-Cre (mean = 71.2; SD = 14.3) were much lower than eGFR_CKD-EPI-2021 (mean = 94.2; SD = 12.7), while eGFR_JPN-Cys (mean = 102.8; SD = 24.2) was comparable to the MDRD and CKD-EPI formulas. The difference between eGFR_CKD-EPI-2021 and eGFR_JPN-Cre showed a V-shaped distribution across eGFR levels, indicating complex errors between these formulas. We observed very low agreement in CKD classification between eGFR_JPN-Cre and the eGFR_CKD-EPI-2021 (kappa = 0.13; 95% confidence interval: 0.06, 0.23).

JPN-Cre was substantially different from the CKD-EPI formula without race term (CKD-EPI-2021), which means that it is impossible to recalibrate those with a simple coefficient. Although a comparison with measured GFR should be necessary, choice of the estimation method needs caution in clinical decision-making and academic research.