Serum potassium concentration ≥5.0 mEq/L was associated with all-cause mortality, CVD death, and non-CVD death in community-living individuals; associations were stronger in diuretic users. Whether maintenance of potassium within the normal range may improve clinical outcomes requires future study.

It is important to accurately assess the glomerular filtration rate (GFR) of patients with liver disease in order to deliver care and allocate organs for transplantation in a way that improves outcomes. The most commonly used methods to estimate GFR in this population are based on creatinine, which is biased by these patients’ low creatinine production and potentially by elevated serum bilirubin and decreased albumin levels. None of the creatinine based estimated GFR (eGFR) equations have been specifically modified for a population with liver disease, and even measurement of a 24 hour creatinine clearance has limitations. In liver disease, all creatinine based estimates of GFR overestimate gold standard measured GFR (mGFR), and the degree of overestimation is highest at lower mGFR values and in more severe liver disease. Cystatin C based eGFR has shown promise in general population studies by demonstrating less bias than creatinine based eGFR and improved association with clinically important outcomes, but results in the liver disease population have been mixed and further studies are necessary. Ultimately, specific eGFR equations for liver disease or novel methods for estimating GFR may be necessary. However, for now, the limitations of currently available methods need to be appreciated to understand renal function in liver disease.

Objectives Both fibroblast growth factor 23 (FGF-23) and frailty have been previously associated with components of bone mineral metabolism, chronic disease states, and mortality. We sought to evaluate whether FGF-23 is related to frailty and to characterize the nature of their joint association with mortality. Design Cross sectional analysis and Cox proportional hazards mortality analysis. Setting The Cardiovascular Health Study Participants 2,977 community dwelling individuals. Measurements The predictor was serum FGF-23 concentration (C-terminal ELISA assay) and the outcomes were frailty status (determined by frailty phenotype criteria of weight loss, weakness, exhaustion, slowness, and decreased physical activity) and mortality. Multinomial logistic regression was used to assess the cross-sectional association of FGF-23 with frailty and prefrailty, adjusting for demographics, cardiovascular disease and risk factors, and kidney markers. Proportional hazards regression was used to assess the association of FGF-23 and frailty with all-cause mortality. Results The mean age was 78 years (SD 4.7), 40% were male, 83% were Caucasian and mean eGFR was 64 ± 17 ml/min/1.73m2. The median FGF-23 value was 70.3 RU/mL [IQR 53.4–99.2]; 52% were prefrail and 13% were frail. After multivariate adjustment, each doubling in FGF-23 concentration was associated with 38% (95% CI 17–62%) higher odds of frailty vs. nonfrailty and 16% (3–30%) higher odds of prefrailty. FGF-23 (HR 1.16; 95% CI 1.10–1.23) and frailty (HR 1.82; 1.57–2.12) were independently associated with mortality, but neither association was meaningfully attenuated when adjusted for the other. Conclusion In a large cohort of older adults, higher FGF-23 was independently associated with prevalent frailty and pre-frailty. FGF-23 and frailty were independent and additive risk factors for mortality. FGF-23 may be a marker for functional outcomes.