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Pernicious Anaemia Society
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intrinsic factor antibody test

Hi, just had another round of blood tests my anti body test was 1,11 U/ml which registered as negative because normal is 1,2 but does that still mean I have a significant amount of antibodies in the blood?

I've also read the test could be altered if you are supplementing b12 (I've had 6 loading doses and am now on 3 a week)

Thank you!

2 Replies

That is a negative result, but the test is not accurate - only about 40-60% accurate. So a negative result doesn't mean that you don't have P.A., just that the test did not find high levels of antibodies at that time. Normally, a positive result will be a lot higher than the reference range. Mine was 30 at diagnosis. A recent injection can alter the results, but will normally give a false positive rather than negative.


if you are supplementing then that can cause false positives. The time from supplementation varies depending on the assay method - for some tests it can be as little as 24-48 hours.

As topazrat says - a negative result is a long way from proving that PA isn't the cause of your B12 absorption problems though a positive would be a good indication that PA is the problem.


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