# Comparison of the applicability of seven calculation equations of glomerular filtration rate among elderly people in China

## TL;DR

This study compares seven equations for estimating kidney function in elderly Chinese patients and finds the BIS1 equation to be the most accurate.

## Contribution

The study identifies the BIS1 equation as the most accurate for estimating glomerular filtration rate in elderly Chinese individuals.

## Key findings

- The BIS1 equation showed the best accuracy with the lowest interquartile range and root-mean-square error.
- All equations underestimated true GFR when measured GFR was below 30 ml/min/1.73 m².
- Bland–Altman plots confirmed the BIS1 equation had the narrowest 95% confidence interval.

## Abstract

At present, estimated glomerular filtration rate (eGFR) remains the most frequently utilized parameter in the evaluation of kidney injury severity. Numerous equations have been formulated based on serum creatinine (Scr) or serum cystatin C (Cysc) levels. However, there is a lack of consensus regarding the efficacy of these equations in assessing eGFR, particularly for elderly individuals in China. This study aimed to evaluate the applicability of the MDRD, MDRDc, CKD-EPI series, BIS1, and FAS equations within the Chinese elderly population.

A cohort of 298 elderly patients with measured GFR (mGFR) was enrolled. The patients were categorized into three subgroups based on their mGFR levels. The eGFR performance was examined, taking into account bias, interquartile range (IQR), accuracy P30, and root-mean-square error (RMSE). Bland–Altman plots were employed to verify the validity of eGFR.

The participants had a median age of 71 years, with 167 (56.0%) being male. Overall, no significant differences in bias were observed among the seven equations (P > 0.05). In terms of IQR, P30, and RMSE, the BIS1 equation demonstrated superior accuracy (14.61, 72.1%, and 13.53, respectively). When mGFR < 30 ml/min/1.73 m2, all equations underestimated the true GFR, with the highest accuracy reaching only 59%. Bland–Altman plots indicated that the BIS1 equation exhibited the highest accuracy, featuring a 95% confidence interval (CI) width of 52.37.

This study suggested that the BIS1 equation stands out as the most applicable for estimating GFR in Chinese elderly patients with normal renal function or only moderate decline. 2020NL-085-03, 2020.08.10, retrospectively registered.