Tested positive for intrinsic factors however blood was taken 2 hours after my first b12 injection...

[Ctb567]

My gastroenterologist said that testing after the injection should be fine, the specialist nurse said it should be fine and so did the nurse giving the jabs but now that I've actually tested positive for it I'm unsure. Just to be clear it was my first ever b12 injection and I had had a b12 injection 2 hours before them taking the blood. Is this test accurate?

I'm just so beyond irritated with the doctors. Ever since I had my low b12 result I have been pushing and pushing to get this test done but every doctor was so unhelpful, it wasn't until I saw this nice specialist nurse that I actually got the test done but now I don't think its accurate or maybe I'm just upset that I'm going to have a lifelong condition :/

Can anyone give any advice? How possible is it that this test is accrurately positive. I have a family history of hypothyroidism and Coeliacs which I think increases the likelihood.

Thanks

[Hidden]

Hi Carly,

The IF test is notoriously unreliable, but if you test positive then you have a 100% diagnosis of PA. I do not know if testing 2 hours after a B12 jab is going to affect that result that much. Some have tested positive then negative then positive again, its just not a terribly accurate test. But if I were you I'd not worry to much, at least testing positive means you will never be taken off B12 injections (I hope), and what ever hope you may have had of not needing B12 injection for life may be lost now, but quite frankly with or with out that result you would have likely needed B12 for life anyway. Its just not that easy to become B12 def.

Can understand the for life bit is not nice, but hey, its not that bad, far worse things to have for life I'm sure!

Kind regards,

Marre.

[Galixie]

The intrinsic factor antibody test would not be affected, whether you have just gotten a B12 injection or not. The test is looking to see if your body's immune system is fighting against the presence of intrinsic factor. Intrinsic factor is a protein that allows the body to absorb B12 and it is made by the parietal cells of the stomach lining. Having B12 in your system (whether through injection or sublingual methods) doesn't affect how your immune system is fundamentally reacting. That is why testing positive for intrinsic factor antibodies (which is the one test that is specifically able to diagnose pernicious anemia) is absolute proof that you do have PA.

Marre is right that the antibody test does give many false-negatives (people who have PA often test negative for the antibodies), but it gives very few false-positives. You could ask to have the test re-run to eliminate the chance of laboratory error, but it seems very likely that your positive result is correct.

[Chancery]

You don't need to worry about the proximity of your injection to the IF antibody test - the two things are not related as far as testing goes. The antibodies will be there no matter how much B12 you have or don't have. So if you have them you have them. B12 won't make them go away, nor does it make them occur - they are quite separate.