Older adults with low creatinine, cystatin C-based eGFR at higher risk for poor outcomes
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Key takeaways:
- Overall, 9,654 patients died of cardiovascular events and 841 died due to kidney failure in the study.
- Counting initial events only, there were 51,096 hospitalizations.
Older adults with low eGFR based on creatinine and cystatin C levels may be at higher risk for adverse events compared with those who have low eGFR based on creatinine level, data show.
“In routine clinical practice, GFR is usually estimated from serum creatinine level (eGFRcr),” lead researcher Edouard L. Fu, PhD, of the department of medical epidemiology and biostatistics at Karolinska Institute in Stockholm, wrote in a study published in the Annals of Internal Medicine.
While an eGFRcr below 60 mL/min/1.73 m2 may be common in older adults, Fu and his colleagues wrote, “levels of 60 mL/min/1.73 m2 or lower are less strongly associated with adverse outcomes in older adults than in young persons ... leading to debate about the appropriateness of the current GFR threshold to define CKD in older adults.”
Researchers conducted a population-based cohort study in Stockholm from 2010 to 2019 that included 82,154 adults aged 65 years or older who underwent outpatient creatinine and cystatin C testing between 2010 and 2019. Investigators compared the associations between eGFR based on creatinine level and eGFR based on creatinine and cystatin C levels (eGFRcr-cys). Patients were followed until outcome occurrence, death or study conclusion.
Primary outcomes were hazard ratios for all-cause mortality, cardiovascular mortality, kidney failure involving replacement therapy, incidence rate ratios for repeated hospitalization, infection, myocardial infarction or stroke, heart failure and AKI.
Overall, 31,219 patients died during follow-up. Of these, there were 9,654 cardiovascular deaths and 841 patients who progressed to kidney failure with renal replacement therapy and died. Counting initial events only, there were 51,096 hospitalizations; 26,754 involving infections; 16,074 due to heart failure; 8,549 related to myocardial infarction or stroke and 5,014 because of AKI.
Findings showed the associations between eGFRcr-cys and outcomes were monotonic, while associations for eGFRcr had a U-shaped pattern, indicating that low eGFRcr-cys was more strongly tied to adverse outcomes compared to low eGFRcr. Researchers found the adjusted hazard ratios for all-cause mortality were 1.2 for eGFRcr-cys and 1 for eGFRcr when comparing 60 mL/min/1.73 m2 vs. 80 mL/min/1.73 m2. These results were similar within study subgroups, including patients with a urinary albumin-creatinine ratio below 30 mg/g.
“Low eGFRcr-cys was more strongly associated with a broad range of outcomes than low eGFRcr among older patients, including all-cause and cardiovascular mortality and many specific types of hospitalizations,” Fu, also of the pharmacoepidemiology and pharmacoeconomics divisions at Brigham and Women’s Hospital and Harvard Medical School in Boston, and colleagues wrote. An “eGFRcr above 90 mL/min/1.73 m2 was associated with higher risk, but not eGFRcr-cys or eGFRcys, suggesting the risk may be driven by low creatinine generation and low muscle mass rather than high GFR itself.”
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