Biological variation in the estimated glomerular filtration rate of healthy individuals within 24 h calculated using 2021CKD-EPI equations

Use the MDRD (Modification of Diet in Renal Disease) and 2021 CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation void of race coefficients (CKD-EPI_Crea, CKD-EPI_Cys-C, and CKD-EPI_Crea+Cys-C) to estimate the BV (Biological variation) of eGFR (estimated glomerular filtration rate) within 24 h in a healthy population to help explain future studies using eGFR in the context of a known BV.

Blood samples were collected from 30 healthy subjects at six time points within 24 h. Serum creatinine (S-Crea) and serum cystatin C (S-Cys-C) were measured, and the BV of eGFR was calculated. Outlier and variance homogeneity analyses were performed, followed by CV-ANOVA on trend-corrected data.

The eGFR CV_I for the four equations (MDRD, CKD-EPI_Crea, CKD-EPI_Cys-C, and CKD-EPI_Crea+Cys-C) were 8.39% (7.50–9.51%), 3.90% (3.49–4.42%), 6.58% (5.88–7.46%), and 5.03% (4.50–5.71%), respectively. The corresponding II and RCV_pos/neg values were 0.69, 0.48, 0.51, and 0.31, and (29.30%, − 22.66%), (12.69%, − 11.2 6%), (20.97%, − 17.33%), and (15.88%, − 13.70%), respectively; RCV_{pos /neg} of eGFR was highest in the MDRD equation and lowest in the CKD-EPI _Crea equation. Additionally, the RCV_pos/neg values of the individual was highest in the MDRD equation and lowest in the CKD-EPI_Crea+Cys-C equation; they are (56.51%, − 36.11%) and (5.01%, − 4.77%), respectively.

We present data on the 24 h BV eGFR of the 2021 CKD-EPI equations. The presence of BV has impact on the interpretation of GFR results, affecting CKD disease grading. The RCV_pos/neg differences were large among the individuals. When using eGFRs based on the MDRD and CKD-EPI equations, it is necessary to combine RCV_pos/neg values before interpreting the results.