2010 Volume 43 Issue 9 Pages 769-777
An increased serum undercarboxylated osteocalcin (ucOC) level is evidence of vitamin K (VK) deficiency. In patients with osteoporosis, the ucOC cut-off value for VK treatment has been clarified. However, in hemodialysis patients, the serum ucOC level is extremely high, and the cut-off value has not yet been determined. Therefore, the ucOC cut-off value for VK treatment was examined in hemodialysis patients. Serum VK, ucOC, osteocalcin (OC), and intact parathyroid hormone (iPTH) levels were examined before VK treatment, and the effects of VK treatment for 3 months on serum ucOC, OC, and iPTH levels were evaluated in 54 hemodialysis patients. These patients were stratified into groups demonstrating serum VK levels <2.36 ng/mL (VK deficiency) and ≥2.36 ng/mL (VK sufficiency). Using receiver operating characteristic (ROC) curve analysis, the optimal ucOC cut-off level that was able to detect a serum VK level 2.36 ng/mL was 35.9 ng/mL. In 32 patients with VK deficiency, the serum ucOC level decreased significantly from a baseline value of 57.7±54.4 ng/mL to 39.3±29.8 ng/mL after 1 month of VK treatment and 40.9±35.30 ng/mL after 3 months (p<0.01), but serum OC and iPTH values did not show any significant changes throughout this period. Therefore, we considered that decrease of the ucOC level after VK treatment indicated VK recovery. Moreover, since the ucOC level showed no significant change between, VK was considered repleted in 1 month after VK treatment. In 32 patients with VK deficiency, using ROC curve analysis to compare ucOC levels before and after 1 month of VK treatment, the optimal cut-off ucOC level to judge VK repletion after VK treatment was 36.2 ng/mL. In patients with baseline ucOC levels ≥35 ng/mL, the ucOC level decreased significantly from a baseline value of 73.5±49.7 ng/mL to 50.9±26.1 ng/mL (p<0.01) after 1 month. Almost the same ucOC cut-off values were derived from examinations of serum VK values before VK treatment and from the ucOC level changes after VK treatment. Hemodialysis patients with serum ucOC levels ≥35 ng/mL appear to be suitable candidates for VK treatment.
