Confused with my Intrinsic Factor Antibody test results

[emvj]

Hi lovely members!

I was told that my B12 was normal, and my Intrinsic Factor antibodies were normal. So I was relieved. But reading into the results, I am less confident in their opinion. In short my antibody level is 1.9 u/mL. Is this just "unit per mililitre"? I have read that anything above 1.53 AU/mL is deemed positive for pernicious anaemia. Am I right about this? I expect I am paranoid right now but surely these measurements are seemingly written up the same? Oh boy. I cannot bear over analysing everything but errors have been so frequently experienced that experience makes it necessary.

[Annnon58]

Hi Emvj , it might be worth asking the GP receptionist for a print out of your IF and b12 results , ranges for IF vary so the print out would say the result and range . Even a negative result doesn’t rule out PA . A “ Normal “ b12 result doesn’t rule out deficiency as it could be borderline . Hope you manage to get a print out to post on here for admin to comment on . Good luck

[emvj in reply to Annnon58]

HI Annnon, I will see what I can get from systemonline. I hope that will be usable. Thank you for your advice and well wishes. All the best!

[Gambit62 Administrator]

Did the test result come with a range?

Although AU/ml and U/ml may be the same I'd be a bit wary of making that assumption and would want to double check that we aren't comparing apples and pears.

Different labs can use different tests and these will have different sensitivities - so what would apply with one lab/test may not translate to another lab and test

The IFA test is known to be lacking in sensitivity anyway - giving false negatives 40-60% of the time - meaning that a negative is a long way from demonstrating that you don't have PA anyway. Its quite a specific test which means that a false positive is rare so a positive result is good evidence of PA.

[helvella in reply to Gambit62]

AU/mL

Absorbance units per milliliter

questdiagnostics.com/hcp/in...

A good look around found the above. This would appear to categorically rule out equivalence to International Units. Over on Thyroid UK we are forever dealing with significantly variable units and ranges. The only sensible approach is to use the reference range from the laboratory that did the test. Anything else could be grossly misleading.

For example, I have seen antibody test results which are scaled so that 0 to 100 is negative, 101 to 200 is some sort of borderline/questionable and over 200 is positive.