Diagnosis - Vitamin B12 or folate deficiency anaemia

[helvella]

The public-facing NHS England page about Diagnosis - Vitamin B12 or folate deficiency anaemia includes this:

A particular drawback of testing vitamin B12 levels is that the current widely used blood test only measures the total amount of vitamin B12 in your blood.

This means it measures forms of vitamin B12 that are "active" and can be used by your body, as well as the "inactive" forms, which cannot.

If a significant amount of the vitamin B12 in your blood is inactive, a blood test may show that you have normal B12 levels, even though your body cannot use much of it.

nhs.uk/conditions/vitamin-b...

I was somewhat surprised that it is quite a strong statement.

Fell across this as I'd actually just been wondering if any of the current B12 assays are affected by patients taking biotin, especially high-dose biotin, prior to a B12 test. Anyone know?

FlipperTD

[FlipperTD]

Scientist, not medic.

I wonder who exactly has written this? It reads a bit like an advert for a test!

The 'Total B12' as in 'Serum B12' assay does just that. The 'Active B12' measures that part which can be used. The ratio of 'Total' to 'Active'is around 4 to 1, and the reference ranges used by laboratories reflect this.

I think it's unlikely that biotin will affect measurement of B12, but given there are numerous methods in use, I can't be certain.

[mickeymouse42 in reply to FlipperTD]

Dr Harrington in his PA Society presentation of 2016 pernicious-anaemia-society.... talks about the Active B12 and Total Serum B12 tests. It's really worth listening to. He is a coauthor of this BMJ B12 article which represents the views of Guy's hospital: bmj.com/content/349/bmj.g52...

The problem is that these views are not necessarily promoted by CCGs or used by GP practices.

It's down to a structural problem where NICE is a guidance organisation; each CCG then produces their guidelines on a whole raft of other subjects. A CCG engages a committee of clinicians to construct these guidelines, introducing different reference ranges and sometimes losing the semantics of the original thinking.

It's not just the B12 guidelines that are different everywhere; the Vit D guidelines have taken a hammering by this process.

Merging NICE and MHRA, scrapping these CCG guidelines and ensuring the guidelines are only written by the top Universities (KCL, UCL, Imperial and other Russell Group Universities) would save a ton of money and rescue us from a Post code lottery.

You can buy the Active B12 test but from the Spire but it costs an arm and a leg; many GPs won't recognise the cheaper tests. Dr Harrington is the clinical director of Viapath Nutris (nutris.viapath.co.uk/) where you can get a reasonably priced Active B12 test that any GP will accept but it's currently not running a postal service; you have to go to Guys' for the phlebotomy service - not so good if you live in Cumbria.

[helvella in reply to mickeymouse42]

Beyond that, even NICE confuses. It has it Clinical Knowledge Summaries (CKS) which, although now being managed by NICE were inherited, and official guidelines.

The status of CKS is not the same as that of full guidelines.

And the British National Formulary (BNF), also now published under the NICE umbrella, is also there to deepen confusion.

[FlipperTD in reply to mickeymouse42]

Thank you!

[Gambit62 Administrator in reply to mickeymouse42]

Personally I would not be in favour of any merger of NICE and MHRA - they have different functions - NICE provides recommendations whilst the MHRA regulates and needs to be independent. I'm not saying the MHRA is perfect because it isn't but I do think that merging the two would not be in the interests of anyone.

[mickeymouse42 in reply to Gambit62]

The SehCat test used in the UK to test for Bile Acid Malabsorption (BAM) is banned in America by the FDA; BAM is closely associated with SIBO and is a key thing to test for when you have gut problems.

I contacted both NICE and MHRA about what their thoughts were on this test and they referred me to each other. The MHRA ventured no further thoughts; NICE were a bit more interested and said that they would conduct a review of the test at a later date. Neither were willing to contact the FDA for its thoughts.

The key point is that there needs to be one source of truth on B12 (BCSH) - it's makes no sense that the 100 or so CCGs develop their own guidelines. B12 diagnosis and treatment should not differ between Lambeth and Luton.

[Gambit62 Administrator]

I had a look at the chemical properties section of pubmeds. I know that biotin can affect the results of thyroid assays - looks like this may be because IR spectrum for the two are very similar so if that is being used in the assay method it is going to get confused. There didn't seem to be any similar correlation with any properties of cobalamin and biotin which would imply it would be unlikely to have any impact - I've certainly not come across anything around interactions between supplementing biotin and cobalamin.This is link to the page on cobalamin

pubchem.ncbi.nlm.nih.gov/so...

[helvella in reply to Gambit62]

Thanks.

The issue with the thyroid tests is that a number use streptavidin in the immunoassay. Biotin binds extremely readily to streptavadin and can affect the result.

I think it was first reported in patients who were using high (really, very high) biotin intake as a possible treatment for Multiple Sclerosis.