Association of Low Glomerular Filtration Rate With Adverse Outcomes at Older Age in a Large Population With Routinely Measured Cystatin C.

The commonly accepted glomerular filtration rate (GFR) threshold used to define chronic kidney disease is based on associations between estimated GFR (eGFR) and the frequency of adverse outcomes. However, the appropriateness of the threshold in older adults is uncertain, partly because the studies measuring these associations included relatively few outcomes and estimated GFR on the basis of creatinine level (eGFR cr), which may be less accurate in older adults. This study evaluated associations between eGFR cr versus eGFR based on creatinine and cystatin C levels and 8 outcomes in older adults. Visual Abstract. Association of Low Glomerular Filtration Rate With Adverse Outcomes at Older Age in a Large Population With Routinely Measured Cystatin C: The commonly accepted glomerular filtration rate (GFR) threshold used to define chronic kidney disease is based on associations between estimated GFR (eGFR) and the frequency of adverse outcomes. However, the appropriateness of the threshold in older adults is uncertain, partly because the studies measuring these associations included relatively few outcomes and estimated GFR on the basis of creatinine level (eGFR cr), which may be less accurate in older adults. This study evaluated associations between eGFR cr versus eGFR based on creatinine and cystatin C levels and 8 outcomes in older adults. Background: The commonly accepted threshold of glomerular filtration rate (GFR) to define chronic kidney disease (CKD) is less than 60 mL/min/1.73 m 2. This threshold is based partly on associations between estimated GFR (eGFR) and the frequency of adverse outcomes. The association is weaker in older adults, which has created disagreement about the appropriateness of the threshold for these persons. In addition, the studies measuring these associations included relatively few outcomes and estimated GFR on the basis of creatinine level (eGFR cr), which may be less accurate in older adults. Objective: To evaluate associations in older adults between eGFR cr versus eGFR based on creatinine and cystatin C levels (eGFR cr-cys) and 8 outcomes. Design: Population-based cohort study. Setting: Stockholm, Sweden, 2010 to 2019. Participants: 82 154 participants aged 65 years or older with outpatient creatinine and cystatin C testing. Measurements: Hazard ratios for all-cause mortality, cardiovascular mortality, and kidney failure with replacement therapy (KFRT); incidence rate ratios for recurrent hospitalizations, infection, myocardial infarction or stroke, heart failure, and acute kidney injury. Results: The associations between eGFR cr-cys and outcomes were monotonic, but most associations for eGFR cr were U-shaped. In addition, eGFR cr-cys was more strongly associated with outcomes than eGFR cr. For example, the adjusted hazard ratios for 60 versus 80 mL/min/1.73 m 2 for all-cause mortality were 1.2 (95% CI, 1.1 to 1.3) for eGFR cr-cys and 1.0 (CI, 0.9 to 1.0) for eGFR cr , and for KFRT they were 2.6 (CI, 1.2 to 5.8) and 1.4 (CI, 0.7 to 2.8), respectively. Similar findings were observed in subgroups, including those with a urinary albumin–creatinine ratio below 30 mg/g. Limitation: No GFR measurements. Conclusion: Compared with low eGFR cr in older patients, low eGFR cr-cys was more strongly associated with adverse outcomes and the associations were more uniform. Primary Funding Source: Swedish Research Council, National Institutes of Health, and Dutch Kidney Foundation. [ABSTRACT FROM AUTHOR]