Low Serum Creatine Kinase Level Predicts Mortality in Patients with a Chronic Kidney Disease

Background Serum creatine kinase (sCK) reflects CK activity from striated skeletal muscle. Muscle wasting is a risk factor for mortality in patients with chronic kidney disease (CKD). The aim of this study is to evaluate whether sCK is a predictor of mortality and end-stage renal disease (ESRD) in a CKD population. Methods We included 1801 non-dialysis-dependent CKD patients from the NephroTest cohort. We used time-fixed and time-dependent cause-specific Cox models to estimate hazard ratios (HRs) for the risk of death and for the risk of ESRD associated with gender-specific sCK tertiles. Results Higher sCK level at baseline was associated with a lower age, a higher body mass index, and a higher level of 24 h urinary creatinine excretion, serum albumin and prealbumin (p<0.001). Men, patients of sub-Saharan ancestry, smokers and statin users also experienced a higher level of sCK. In a time-fixed Cox survival model (median follow-up 6.0 years), the lowest gender-specific sCK tertile was associated with a higher risk of death before and after adjustment for confounders (Crude model: hazard ratio (HR) 1.77 (95% CI: 1.34-2.32) compared to the highest tertile; fully-adjusted model: HR 1.37 (95% CI: 1.02-1.86)). Similar results were obtained with a time-dependent Cox model. The sCK level was not associated with the risk of ESRD. Conclusion A low level of sCK is associated with an increased risk of death in a CKD population. sCK levels might reflect muscle mass and nutritional status.