Vitamin K exists in multiple forms, which are 2-methyl-1,4-naphthoquinone derivatives. Phylloquinone is the principal form found in green leafy vegetables. Menaquinone-4 (MK-4) is present in animal feed and is also formed from dietary phylloquinone. Both serve as cofactors for the carboxylation of vitamin K-dependent proteins (VKDPs), which include coagulation factors, osteocalcin and bone and matrix Gla proteins. Vitamin K has multiples roles beyond coagulation, and has been investigated in relation to chronic diseases, including osteoporosis and cardiovascular disease (2, 3).
Assessment of vitamin K status.
Patient/subject: Over night fasting is recommended, since plasma phylloquinone fluctuates in accordance with recent dietary intakes, and it is closely correlated with triglyceride concentrations. The subject must abstain form alcohol for 24 hours before blood draw.
Matrix: Serum or EDTA plasma. Avoid hemolysis.
Volume: Minimum volume is 50 µL, but 200 µL is optimal and allows reanalysis.
Preparation and stability: Serum gel tubes must not be used. Samples should be put on ice, and protected from light.
Reported values, phylloquinone: 0.5-20 nmol/L.
Intraclass correlation coefficient (ICC): 0.49.
1. Midttun, Ø., McCann, A., Aarseth, O., Krokeide, M., Kvalheim, G., Meyer, K., and Ueland, P.M. (2016). Combined measurement of 6 fat-soluble vitamins and 26 water-soluble functional vitamin markers and amino acids in 50 μL of serum or plasma by high-throughput mass spectrometry. Anal Chem 88, 10427-436.
2. Fusaro, M., Gallieni, M., Rizzo, M.A., Stucchi, A., Delanaye, P., Cavalier, E., Moysés, R.M.A., Jorgetti, V., Iervasi, G., et al. (2017). Vitamin K plasma levels determination in human health. Clin Chem Lab Med 55, 789-799.
3. Mladěnka, P., Macáková, K., Kujovská Krčmová, L., Javorská, L., Mrštná, K., Carazo, A. et al. (2021). Vitamin K – sources, physiological role, kinetics, deficiency, detection, therapeutic use, and toxicity. Nutr Rev, nuab061.