Discordance in Creatinine- and Cystatin C-Based eGFR and Clinical Outcomes: A Meta-Analysis

Area of Science:

• Nephrology
• Clinical Epidemiology
• Biomarker Research

Background:

• Estimated glomerular filtration rates (eGFRs) are crucial for assessing kidney function.
• Discrepancies exist between eGFR calculated using creatinine (eGFRcr) and cystatin C (eGFRcys).
• The clinical significance and prevalence of these eGFR differences are not well understood.

Purpose of the Study:

• To determine the prevalence of discordance between eGFRcys and eGFRcr.
• To identify patient characteristics associated with significant eGFR differences.
• To assess the association of eGFR discordance with adverse health outcomes.

Main Methods:

• Individual-level meta-analysis of data from the Chronic Kidney Disease Prognosis Consortium (CKD-PC).
• Inclusion of participants with concurrent cystatin C and creatinine measurements and outcome data.
• Definition of a large negative eGFR difference (eGFRdiff) as eGFRcys being at least 30% lower than eGFRcr.

Main Results:

• 11% of outpatients and 35% of inpatients exhibited a large negative eGFRdiff.
• In outpatients, a large negative eGFRdiff was associated with significantly higher rates of all-cause mortality (HR 1.69), cardiovascular mortality (HR 1.61), atherosclerotic cardiovascular disease (HR 1.35), heart failure (HR 1.54), and kidney failure (HR 1.29).

Conclusions:

• A substantial proportion of patients, particularly inpatients, demonstrate significant discordance between eGFRcys and eGFRcr.
• This eGFR discordance, specifically lower eGFRcys, is a significant predictor of adverse outcomes including mortality and kidney failure.
• The findings highlight the clinical importance of evaluating eGFR differences in patient risk stratification.