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Serum indices based on creatinine and cystatin C, including creatinine/cystatin C ratio (Cr/CysC), ratio and difference of estimated glomerular filtration rate (eGFR) based on cystatin C and creatinine (eGFRcys/eGFRcre and eGFRDiff), and serum creatinine × eGFRcys, are recently identified serum markers for sarcopenia. We aimed to evaluate the association between these serum indices and mortality in patients with chronic kidney disease (CKD). A single-center retrospective cohort study included 1141 adult patients with stage 1–5 CKD between 2016 and 2018. Basic characteristics, comorbidities, laboratory parameters, and serum creatinine and cystatin C values were obtained. Patients were followed up until death, dialysis, transfer to another hospital, or end of the study. The median age (interquartile range) of our participants was 71 (62–81) years. During a median follow-up of 39 months, 116 (10.2%) patients died. Compared to the survivor group, Cr/CysC, eGFRcys/eGFRcre, eGFRDiff, and Cr × eGFRcys were all lower in the non-survivors (p < 0.001 for all). The receiver operating characteristic curves of serum indices for predicting mortality showed that all four indices had significant discriminative power. Based on the Cox proportional hazard models, lower values of four serum indices, both as continuous and categorical variables, independently predicted mortality. Our findings suggest that low serum indices of Cr/CysC, eGFRcys/eGFRcre, eGFRDiff, and Cr × eGFRcys are independent indicators of mortality in patients with non-dialysis CKD.

Background. Irisin is a circulating hormone-like myokine that plays an important role in bone metabolism. We performed a cross-sectional study to investigate whether serum irisin levels correlated with bone mineral density (BMD) in patients on maintenance hemodialysis (MHD). Methods. Blood samples were obtained from 80 patients on MHD, and serum irisin concentrations were determined using a commercially available enzyme-linked immunosorbent assay. BMD was measured by dual-energy X-ray absorptiometry of the L2–L4 vertebrae. Results. In the study cohort, 10 (12.5%) and 19 (23.8%) patients had osteoporosis and osteopenia, respectively, and 51 (63.75%) patients had normal BMD. Lumbar T-score was negatively associated with body height ( P = 0.010 ), body weight ( P = 0.002 ), body mass index (BMI, P = 0.010 ), and serum irisin ( P < 0.001 ) and was positively associated with advanced age ( P = 0.031 ), female sex ( P = 0.001 ), alkaline phosphatase (ALP, P = 0.010 ), urea reduction rate ( P = 0.018 ), and fractional clearance index for urea ( P = 0.020 ). Multivariable forward stepwise linear regression analysis revealed that high serum logarithmically transformed irisin (log-irisin, β = 0.450, adjusted R2 change = 0.258; P < 0.001 ), female sex (β = −0.353, adjusted R2 change = 0.134; P < 0.001 ), and serum ALP level (β = −0.176, adjusted R2 change = 0.022; P = 0.049 ) were significantly and independently associated with lumbar BMD in patients on MHD. Conclusions. In addition to female sex and serum ALP level, serum irisin level was positively associated with lumbar BMD in patients on MHD.