Intrinsic antibody test after B12 multivits

[tiredBFmum]

Struggling with clarity on whether I should have the intrinsic antibody test when I have already had some B12 in my multivits? I have never had that test.

The only bit I saw on the PA charity website was 'BE AWARE – taking supplements that contain B12 will affect any tests ordered by your doctor to assess your B12 status. You should not take any supplement before having your B12 assessed and/or having the test to find out if you have the Intrinsic Factor Antibody.' on pernicious-anaemia-society....

I presume that is true but I guess I dont understand why the antibody would disappear if consuming some B12?

If it is worthwhile to have it still, would it be this test? medichecks.com/tests/intrin...

I have rung the PA website and the man was very blunt - he said supplements could take 2 years to leave system and the intrinsic antibody test is pointless. I understand it has very low sensitivity but 95% specificity.

I understand that trialling b12 injections is a possibility in an ideal world but in reality the GP is not going to do this without some more evidence eg blood test results.

Interestingly my fatigue, weakness and dizziness increased after having entonox (gas and air) for a sigmoidoscopy (results clear but had due to severe IBS pain). I have had to take some time off work, been more clumsy and feel "all over the place" /foggy brained. But maybe something else is going on...

[wedgewood]

I can only tell you what happened to me when I had the I.F.A. ( Intrinsic Factor Antibody ) test . I was desperate , so unwell with loads of symptoms and had been sent on my way by my GP .I was taking loads of sub-lingual B12 and my body was covered in B12 patches , when I went to a Nuffield Hospital to a private GP . He did the test and it came back positive , in spite of the loads of B12 I had taken . But yes , it is a very unreliable test , and I was lucky I suppose . .But , as you say , the antibodies do not disappear when you are taking any sort of B12 ., so they shouldn’t be affected . If you have PA , they are with you for life.

[fbirder]

The antibody doesn’t disappear if you’re taking supplements.

If you have too much B12 in your blood then you can get a false positive result. So they can th7nk you’ve got lots of the antibodies even if you haven’t.

Here’s what the Mayo Clinic say...

Do not order intrinsic factor blocking antibody (IFBA) testing in patients who have received a vitamin B12 injection within the last 2 weeks. High free serum vitamin B12 levels, as may be seen within the first 2 weeks after a vitamin B12 injection, can interfere in the IFBA assay, leading to false-positive results. We reflex all positive IFBA tests that have not been ordered through the Pernicious Anemia Cascade to vitamin B12 measurement. If this yields a level >800 ng/L, we append a comment to the report indicating a possible false-positive result.

mayomedicallaboratories.com...

[Curlygal in reply to fbirder]

I checked the immunology guide for the lab that was going to do my test (My immulogist runs the lab so I took a punt and asked if she would test IF antibodies)- and the particular method they use is unaffected by B12 levels being high. This is in Glasgow. If anyone knows the specific lab that will do their test, it might-perhaps- be possible to check this. I think this method/assay is new.

[fbirder in reply to Curlygal]

Yes, the ‘new’ assay should be unaffected. But that assay has only been around 10 years.

[wedgewood]

Well according to fbirders quote from the Mayo Clinic , it’s a B12 injection , within 2 weeks of the test, that could skew the result . I hadn’t had an injection just sub -linguals and patches .

[fbirder in reply to wedgewood]

I would hope that the sublinguals and patches are actually getting stuff into the bloodstream otherwise there seems little point in taking them.

[wedgewood]

Yes, I would have thought so too , but your quote from the Mayo clinic only mentioned B12 injections . So I thought that they knew something that I didn’t .