Total vs Active B12

Vitamin B12, or cobalamin, is a vital water-soluble vitamin that plays an essential role in myelination initiation and development, cellular energy and fatty acid metabolism. It is a cofactor for enzymes methionine synthase and L-methyl-malonyl-coenzyme A mutase and, in addition to folate, is essential for DNA and protein synthesis. In the UK, up to 6% of adults under 60 have been diagnosed with Vitamin B12 deficiency and figures are much higher in elderly populations¹. Additionally, these data do not consider the high rates of missed diagnosis associated with B12 deficiency, which some reports claim to be as high as 26%². New guidance from the National Institute of Health and Care Excellence (NICE) advise that Active vitamin B12 testing is recommended for some groups of patients. In this article, we’ll look at this essential vitamin, B12 deficiency and the associated complications, compare the biomarkers used to diagnose B12 deficiency, and finally, present the new Acusera Active B12 Control.

Aetiology

Vitamin B12 deficiency can arise due to dietary insufficiency, malabsorption resulting from damage to the small intestine, often caused by conditions like Coeliac disease or Crohn’s disease, or via pernicious anaemia – an autoimmune condition which results in an inability to absorb vitamin B12.

It is a common problem in the elderly population – bodily stores of vitamin B12 can take up to 20 years to become depleted, meaning complications have often already begun before diagnosis occurs. The most common source of vitamin B12 comes from dietary intake of animal products therefore vegetarian dietary requirements are considered a considerable risk factor for vitamin B12 deficiency.

Pathophysiology and Complications

Vitamin B12 deficiency significantly impacts health, affecting various bodily functions, potentially leading to a range of complications. Megaloblastic anaemia is a common complication associated with vitamin B12 deficiency and is characterised by the presence of large red blood cell precursors (megaloblasts) in the bone marrow³. The lack of vitamin B12 results in impaired DNA synthesis and an inhibition of nuclear division. However, cytoplasmic maturation is less effected. This results in asynchronous maturation of the nucleus and cytoplasm in erythrocytes and causes the synthesis of abnormally large megaloblasts. This causes the cessation of DNA synthesis and DNA replication errors, culminating in apoptotic cell death. Common symptoms of megaloblastic anaemia include weakness, shortness of breath, palpitations, tachycardia, Hunter glossitis or splenomegaly³.

Pernicious anaemia is a condition commonly associated by vitamin B12 deficiency. Pernicious anaemia is an autoimmune disorder which affects the gastric mucosa resulting in impaired absorption of vitamin B12. Common symptoms of pernicious anaemia include glossitis, hair loss, dry skin, memory loss, poor concentration, poor sleep, confusion and dizziness, shortness of breath, Diarrhoea, indigestion, loss of appetite, mood swings and suicidal thoughts.

Neurological issues may also arise, including numbness, mobility loss, and memory issues, and in some cases, depression⁴. Additionally, B12 deficiency is linked to increased risks of cardiovascular events⁵, infertility⁶, and autoimmune diseases like multiple sclerosis⁷ and lupus⁸. In children, vitamin B12 deficiency can manifest as failure of brain and overall growth and development, developmental regression, hypotonia, lethargy, hyperirritability, or coma⁹.

Active B12 as a marker of Deficiency

There are several markers of vitamin B12 deficiency. The most used in clinical practice are total vitamin B12, homocysteine, methylmalonic acid (MMA), and Holotranscobalamin (HoloTC) – also known as Active B12. HoloTC accounts for between 10-30% of total B12 and is the metabolically active form of vitamin B12.

When compared with total B12 quantification, HoloTC measurement has been shown to be a more sensitive and specific biomarker of B12 deficiency, particularly at borderline clinical levels¹⁰, in various cohorts^11,12 including those on vegan diets¹³ – a known risk factor for B12 deficiency. Furthermore, HoloTC was shown to provide the higher diagnostic accuracy in clinical and subclinical B12 deficiency versus Total B12, MMA and homocysteine with significantly higher accuracy in women over 50¹¹ – a population at high risk of B12 deficiency.

In response to the mounting evidence of the superior utility of HoloTC quantification, the National Institute for Health and Care Excellence (NICE) have produced new guidelines recommending either total B12 or HoloTC for the initial testing of suspected vitamin B12 deficiency. These guidelines specify the use of active B12 during pregnancy and suggest that active B12 might provide a more specific assessment in certain clinical contexts.

Acusera Active B12 Control

For the reasons stated above, Randox are proud to present the Acusera Active Vitamin B12 Control. This control is designed for use with in vitro diagnostic assays for the quantitative determination of HoloTC in human serum and plasma and is suitable for use on a variety of analysers. This true third-party control is provided in a liquid ready-to-use format reducing preparation time and has an impressive 30-day open vial stability, helping to minimise waste. Like all Acusera controls, the Active B12 Control is supplied at consistent, clinically relevant levels to ensure the test system is challenged at the critical decision limits used to aid diagnosis. Furthermore, this control is provided with assayed target values for a range of analysers which are available through our new SmartDocs portal.

Summary of Benefits:

• Dedicated, HoloTC control.
• 30-day Open Stability.
• 2-year shelf life.
• Liquid Ready-to-use.
• Human Serum Based.
• Consistent, clinically significant values.
• True third-party controls.
• Assayed target values.

Ensure the accuracy of your vitamin B12 testing with Randox’s Acusera Active Vitamin B12 Control. Join the other laboratories around the world who trust Acusera to help deliver reliable, clinically relevant test results. Contact us today at marketing@randox.com to learn more and order your supply of the Acusera Active B12 Control.

References

1. Hunt A, Harrington D, Robinson S. Vitamin B12 deficiency. BMJ. 2014;349(sep04 1):g5226-g5226. doi:10.1136/bmj.g5226
2. Oh RC, Brown DL. Vitamin B 12 Deficiency Clinical Manifestations of Vitamin B 12 Deficiency. Vol 67.; 2003. www.aafp.org/afp
3. Hariz A, Bhattacharya PT. Megaloblastic Anemia. StatPerals Publishing; 2024.
4. Patel S V., Makwana AB, Gandhi AU, Tarani G, Patel J, Bhavsar V. Factors associated with vitamin B12 deficiency in adults attending tertiary care Hospital in Vadodara: a case control study. Egypt J Intern Med. 2022;34(1):11. doi:10.1186/s43162-022-00104-0
5. Pawlak R, Parrott SJ, Raj S, Cullum-Dugan D, Lucus D. How prevalent is vitamin B12 deficiency among vegetarians? Nutr Rev. 2013;71(2):110-117. doi:10.1111/nure.12001
6. Green R, Graff JP. Megaloblastic Anemia. In: Atlas of Diagnostic Hematology. Elsevier; 2021:47-51. doi:10.1016/B978-0-323-56738-1.00004-X
7. Najafi MR, Shaygannajad V, Mirpourian M, Gholamrezaei A. Vitamin B(12) Deficiency and Multiple Sclerosis; Is there Any Association? Int J Prev Med. 2012;3(4):286-289.
8. Segal R, Baumoehl Y, Elkayam O, et al. Anemia, serum vitamin B12, and folic acid in patients with rheumatoid arthritis, psoriatic arthritis, and systemic lupus erythematosus. Rheumatol Int. 2004;24(1):14-19. doi:10.1007/s00296-003-0323-2
9. Stabler SP. Vitamin B12 Deficiency. New England Journal of Medicine. 2013;368(2):149-160. doi:10.1056/NEJMcp1113996
10. Bondu JD, Nellickal AJ, Jeyaseelan L, Geethanjali FS. Assessing Diagnostic Accuracy of Serum Holotranscobalamin (Active-B12) in Comparison with Other Markers of Vitamin B12 Deficiency. Indian Journal of Clinical Biochemistry. 2020;35(3):367-372. doi:10.1007/s12291-019-00835-y
11. Jarquin Campos A, Risch L, Nydegger U, et al. Diagnostic Accuracy of Holotranscobalamin, Vitamin B12, Methylmalonic Acid, and Homocysteine in Detecting B12 Deficiency in a Large, Mixed Patient Population. Dis Markers. 2020;2020:1-11. doi:10.1155/2020/7468506
12. Verma A, Aggarwal S, Garg S, Kaushik S, Chowdhury D. Comparison of Serum Holotranscobalamin with Serum Vitamin B12 in Population Prone to Megaloblastic Anemia and their Correlation with Nerve Conduction Study. Indian Journal of Clinical Biochemistry. 2023;38(1):42-50. doi:10.1007/s12291-022-01027-x
13. Lederer AK, Hannibal L, Hettich M, et al. Vitamin B12 Status Upon Short-Term Intervention with a Vegan Diet—A Randomized Controlled Trial in Healthy Participants. Nutrients. 2019;11(11):2815. doi:10.3390/nu11112815