Biologically active vitamin Β12 (cobalamin) is a test based on a microbiological method that measures the total vitamin Β12 content in a blood sample.
What are the benefits of measuring Biologically Active Vitamins?
This test measures the biologically active in vivo metabolites of B vitamins. Vitamins' biological action (bioactivity) has more excellent value. It is a more representative indication of their active concentration than the simple chemical measurement of their levels, especially in cases where these indications are used to determine substitution therapy or to check a therapeutic intervention.
Vitamin B12 (cobalamin), a collective term for a group of various substituted corrinoids with cobalt as the central atom, is found free and protein-bound in food. The protein-bound form is degraded by pancreatic protease, releasing free B12, which binds to intrinsic factor, a protein secreted by gastric parietal cells of the stomach mucosa. The cobalamin-intrinsic factor complex is bound to mucous membrane cells in the ileum and absorbed by the cells. In the case of high doses, a diffusion of the complex also takes place. Vitamin B12 is bound to the cells' protein transcobalamin II (TC-II). TC-II serves as a transport protein for vitamin B12 in the circulation system.
Vitamin B12 is a co-enzyme involved in metabolic processes and plays an essential role in the formation of the blood, the development of the nervous system, and the regeneration of mucous membranes. In addition, methylcobalamin is directly related to forming folic acid because it transfers methyl groups to synthesize methionine from homocysteine.
Vitamin B12 deficiency
Dietary factors rarely cause vitamin B12 deficiency. In most cases, it results from a resorption disorder of the intestines or defective development of intrinsic factors. Since vitamin B12 resorption can be reduced by up to 50% in the elderly, an increased supplement is recommended. The classical vitamin B12 deficiency disease is pernicious anemia. In the early stages of the disease, vitamin B12 deficiency symptoms manifest as weariness, palpitations, pallor, or jaundice.
Indications for vitamin B12 determination
- Megaloblastic (pernicious) anemia
- Hyperhomocysteinaemia (patients on dialysis, old people)
- Homocystinuria
- Peripheral neuropathy
- Patients with chronic diarrhea, gastritis, gastrectomy, gluten intolerance, or intestinal resorption disorders
- Pancreatic insufficiency
- Patients with thrombosis
- Alcoholism
- Chronic liver and kidney disease
- Vitamin B12 deficiency from diet (vegan vegetarians)
- Pregnancy and lactation
How are Biologically Active Vitamins measured?
To test the biologically active vitamins, the blood sample is subjected to an enzymatic pre-treatment and then placed in microplates containing microorganisms sensitive to these vitamins (e.g., Lactobacillus fermentum, Lactobacillus rhamnosus, Lactobacillus leichmanii, Saccharomyces cerevisiae). The nutrient medium, specific and unique to each vitamin, contains all the necessary ingredients for the growth of microorganisms, except for the vitamin to be measured. When the patient's blood is added to the material, the microorganisms grow until the examined vitamin is depleted. The growth of microorganisms is measured after 72 hours of incubation in a particular multi-channel analyzer and compared to standard concentrations of vitamins. The bioactivity of the tested vitamin is directly proportional to the measured growth of microorganisms.
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