# Association of Intraindividual Difference in Cystatin C and Creatinine Estimated Glomerular Filtration Rate With Diabetes

## TL;DR

This study found that a negative difference between two kidney function estimates is linked to higher diabetes risk in older Chinese adults.

## Contribution

The study identifies eGFRdiff as a novel marker for diabetes risk independent of overall kidney function.

## Key findings

- A negative eGFRdiff was associated with higher odds of diabetes after adjusting for kidney function measures.
- The association remained significant when controlling for creatinine- and cystatin C-based eGFR separately.
- The findings suggest eGFRdiff could be a useful indicator of metabolic health.

## Abstract

Declined renal function is closely linked to diabetes. However, it remains unclear whether the intraindividual difference between cystatin C- and creatinine-based estimated glomerular filtration rates (eGFRdiff) is associated with diabetes. This study was aimed at examining the association between eGFRdiff and prevalent diabetes in a nationally representative cohort of Chinese adults.

We analyzed data from 11,869 adults aged ≥ 45 years participating in the China Health and Retirement Longitudinal Study (CHARLS), including 2279 individuals with diabetes. We calculated eGFRdiff as the absolute difference between cystatin C- and creatinine-based eGFR levels. Multivariable logistic regression and restricted cubic spline models were used to assess the association between eGFRdiff and prevalent diabetes. Subgroup analyses were conducted on sex, body mass index, hypertension status, and creatinine-based eGFR status.

The mean participant age was 60.3 (±9.6) years, and 53.5% were female. Participants were categorized into three groups based on eGFRdiff: midrange (−15 to 15 mL/min/1.73 m2, 67.9%), negative (<−15, 22.7%), and positive (> 15, 9.4%). Compared to the midrange group, individuals in the negative eGFRdiff group had a significantly higher odds of diabetes, even after adjusting for the creatinine-based eGFR (OR: 1.21, 95% CI: 1.08–1.36) and cystatin C-based eGFR (OR: 1.32, 95% CI: 1.16–1.50).

In this large, community-based population, a negative eGFRdiff—where cystatin C-based eGFR is substantially lower than creatinine-based eGFR—is associated with a higher prevalence of diabetes, independent of overall kidney function. These findings suggest that eGFRdiff may serve as a novel marker for metabolic status.