Suboptimal vitamin K status and its risk factors in a population of Chinese chronic haemodialysis patients.

Abstract

Vitamin K deficiency is known to be common in haemodialysis patients and associates with adverse outcomes in this population, particularly vascular calcification. We aimed to investigate the vitamin K status in a population of Chinese haemodialysis (HD) patients. We collected demographic and biochemical data from a population of maintenance HD (MHD) patients in our unit and a control group composed of healthy subjects from our outpatient clinic. Fasting serum samples from all subjects were collected for the measurement of known vitamin K-dependent proteins i.e. matrix Gla protein (MGP), osteocalcin (OC) and uncarboxylated osteocalcin (ucOC). We also quantified the fraction of ucOC to total OC (%ucOC). Differences of these parameters between groups were analyzed and risk factors of vitamin K deficiency based on the definition as per %ucOC were investigated. We enrolled 93 MHD patients as a test group and 93 healthy subjects as a control group. There was no significant difference in MGP between groups (4.0 ± 2.8 pg/mL in MHD vs 4.2 ± 1.2 pg/mL in control; P = 0.676). Mean %ucOC was significantly greater in the MHD patients as compared to control subjects (76.4 ± 20.0% in MHD vs 48.56 ± 15.5%; P < 0.001). Time on dialysis and low-density lipoprotein cholesterol level appeared to be indicators of vitamin K deficiency, with the former being an independent risk factor. Defining Vitamin K deficiency by %ucOC, suboptimal vitamin K levels appear common in Chinese MHD patients. Time on dialysis and LDL cholesterol level predict vitamin K deficiency.