Discordance between cystatin C-based and creatinine-based estimated glomerular filtration rate and mortality in the general population

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Original Article: https://doi.org/10.1093/clinchem/hvaf063

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Abstract

Background

The consequences for health outcomes of the discordance in cystatin C-based (eGFR_cys) and creatinine-based (eGFR_cr) estimated glomerular filtration rates are gaining attention. However, the association of discordance with all-cause mortality in the general population has not been explored.

Methods

A total of 325 356 UK Biobank participants, 40 to 69 years-of-age, were followed for a median of 13.7 years. eGFR was calculated using both the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) 2009/2012 equations and the European Kidney Function Consortium (EKFC) equations. Differences were expressed as the absolute difference (eGFR_cys − eGFR_cr, where discordance was defined as ±15 mL/min/1.73 m² difference) and relative difference (eGFR_cys/eGFR_cr, where discordance was defined as eGFR_cys < 60% eGFR_cr). Hazard ratios (HRs) for mortality were estimated using multivariable Cox proportional hazards models.

Results

Among the participants, 15.5% had a discordant lower absolute eGFR_cys, and 8.5% had a discordant higher absolute eGFR_cys. Participants with discordant lower absolute eGFR_cys (both CKD-EPI and EKFC equations) were older, more frequently male, had higher body mass index (BMI) and blood pressure, more comorbidities, and did less physical activity. A total of 26 465 deaths occurred. Participants with discordant lower eGFR_cys had a 53% higher risk of mortality (HR = 1.53: 95% CI, 1.48–1.57), while those with discordant higher eGFR_cys had a 30% lower risk (HR = 0.70: 95% CI, 0.66–0.75) compared to those with concordant eGFR. Those with discordance of lower relative eGFR_cys had doubled risk of mortality (HR = 2.25: 95% CI, 2.04–2.47).

Conclusions

eGFR discordance was prevalent and associated with mortality in general populations. These results support broader use of cystatin C for risk stratification of mortality.