Cystatin C- and Creatinine-based Estimated GFR Differences: Prevalence and Predictors in the UK Biobank

Large differences between estimated glomerular filtration rate (eGFR) based on cystatin C (eGFRcys) and creatinine (eGFRcr) occur commonly. A comprehensive evaluation of factors that contribute to these differences is needed to guide the interpretation of discrepant eGFR values. Cohort study. 468,969 participants in the UK Biobank. Candidate sociodemographic, lifestyle factors, comorbidities, medication usage, and physical and laboratory predictors. eGFRdiff, defined as eGFRcys minus eGFRcr, categorized into 3 levels: lower eGFRcys (eGFRdiff, less than−15mL/min/1.73m2), concordant eGFRcys and eGFRcr (eGFRdiff, −15 to300mg/g. Odds ratio estimates for these predictors were largely inverse of those in the lower eGFRcr group. The model’s area under the curve was 0.75 in the validation set, with good calibration (1.00). Limited generalizability. This study highlights the multitude of demographic, lifestyle, and health characteristics that are associated with large eGFRdiff. The clinical model may identify individuals who are likely to have discrepant eGFR values and thus should be prioritized for cystatin C testing. Estimated glomerular filtration rate (eGFR) based on cystatin C and creatinine may differ substantially within an individual. Although most clinicians are aware that creatinine is influenced by muscle mass, there are additional numerous lifestyle and health characteristics that may affect serum concentrations of either biomarker. Our analyses of 468,969 individuals in the UK Biobank identified independent predictors of large