About vitamin B12 - Vitamin B12 has the largest and most complicated structure of all the vitamins. In the centre of this structure is a cobalt ion, hence the term cobalamin is used for any compound possessing vitamin B12 activity.
Vitamin B12 is synthesised by micro-organisms and enters the food chain in food of animal origin.
To detect patients with vitamin B12 deficiency at the earliest opportunity, GSTS offers; ‘Active’ vitamin B12
(holotranscobalamin), a new laboratory marker which replaces the serum vitamin B12 test. ‘Active’ vitamin B12 minimises repeat or inappropriate testing that can occur as a result of the, less effective serum vitamin B12 test which has been recognised as being a relatively late marker.
What GSTS offers - It is well known that the diagnosis of vitamin B12 deficiency is problematic. Current assays tend to measure total vitamin B12 which leads to a large grey area where deficient patients can be missed. This is because for this vitamin there is a poor correlation between circulatory levels of total vitamin B12 and actual status at the tissue level. Conversely, patients can be inappropriately classified to a deficient state with the inconvenience and expense of long term supplementation regimes.
GSTS now offers the ‘Active’ vitamin B12 (holotranscobalamin) assay which complements our popular serum methylmalonic acid (MMA) assay; a functional marker of B12 status. Holotranscobalamin is the metabolically active portion of vitamin B12 and low levels in the circulation is thought to be the earliest laboratory indicator of a negative vitamin B12 balance.
B12 Deficiency - Vitamin B12 deficiency is common (especially in people over the age of 60). It also occurs in patients with
autoimmune disease (pernicious anaemia), severe primary hypothyroidism, those with ileal disease, patients on chronic therapy with antacids, proton pump inhibitor (PPI) or H2 antagonists, or colchicine, and in chronic malnutrition states including alcoholism. Other causes include vegetarian or vegan diets, pregnancy and lactation.
The timely detection, and correction, of vitamin B12 deficiency prevents macrocytic anaemia, elevated circulatory levels of homocysteine (thrombotic risk factor), potentially irreversible peripheral neuropathy, memory loss and other cognitive deficits.
Deficient states induced by poor dietary intake (i.e. vegetarian or vegan diets), take up to 20 years to manifest. However, clinical deficiencies as a consequence of abnormalities in one of the multiple steps that regulate cobalamin absorption or enterohepatic circulation present more rapidly (~2 years).
Ultimately, intestinal uptake of vitamin B12 takes place in the ileum by a receptor mediated process that includes the calcium dependant binding of a vitamin B12/intrinsic factor complex. After absorption of vitamin B12/intrinsic factor complex into the enterocytes, the complex is degraded and liberated vitamin B12 is transported into the blood where it binds to transcobalamin forming holotranscobalamin - ‘Active’ vitamin B12. Transcobalamin transports vitamin B12 to
the cells of the body.
What to do - Patients wishing to have the ‘Active’ vitamin B12 test must request it from their GP who can either take
the sample themselves, or refer the patient to one of GSTS’ phlebotomy departments at St Thomas’ or King’s College Hospital, London. Please note that if the patient is referred, they must attend the phlebotomy department with a referral letter signed by their GP or the test cannot be performed.
Integrity of sample – Samples must be taken and transported in the correct way in order to ensure the integrity of the sample. If this is not done, the results could be affected. Please refer to the sample transport page on our website at
http://www.gsts.com/sample-transport . This will provide necessary information on how to send samples, ensuring they are processed quickly by our Central Specimen Reception team.
Sample requirement – Venous blood should be collected into serum tubes (yellow top). Other sample types are not suitable. Before shipping, it is recommended that specimens be removed from the clot. Serum may be shipped ambient (maximum 16 hours in transit), at +2-8°C (wet ice) - stable for up to three days, or frozen (dry ice). The minimum sample
volume required to perform this assay is 200μl.
Advice – We provide expert interpretation of results to ensure your patients are being given the correct advice. GSTS scientists work closely with Clinicians to ensure the best advice and interpretation is provided for each result.
Turnaround time – The turnaround time for the ‘Active’ vitamin B12 assay is within 10 days from receipt of the sample.
Please note: ‘Active’ vitamin B12 concentrations <25 pmol/L indicate vitamin B12 deficiency. For results between 25-34 pmol/L a confirmatory functional assay of vitamin B12 status, namely methylmalonic acid (MMA) will be performed to confirm status.
JacYour serum b12 was 363 but Active only 19
JDee wrote:Renie451 resultsJacYour serum b12 was 363 but Active only 19
renie451 wrote:just recieved Cyno tabs
And still this goes on!!!! DiabolicalP.S. As the test went to my GP I was initially advised that all the tests were OK (negative) it was only when I insisted on getting a copy of the actual test results from the GSTS labs that the GP acknowledged that my MMA test was High and that GSTS had actually provided a diagnosis of B12 deficiency! So PLEASE ensure you insist on getting a copy of the GSTS tests results if you undertake these tests as we unfortunately can't trust our GP's to provide the correct results/diagnosis. I am still waiting for my GP practice to advise me what treatment /referral they intend to action following these results!!
Users browsing this forum: No registered users and 6 guests