Help understanding PA lab result?

[hani0902]

Hi!

I had an antibody test for pernicious anemia and I can't read the lab results well... my antibody level says 2.15 and the comparison levels are NEGATIVE = <20.0 EQUIVOCAL = 20.1 - 24.9 POSITIVE = >25. Are these in the same units? Would this be a positive or negative test? I am currently having neurological symptoms and am just about to finish my two weeks of B12 loading doses. My doctor, dispite having this result already, said he hadn't tested the intrisic factor yet... so I am yet to hear his interpretation. I'm also 20 with hypothyroidism if that makes any difference!

Thank you in advance!

[hani0902]

Just to add on, I have seen that 2.15 is in u/mL

[Foggyme Administrator]

Hani0902

< means less than and > means greater than so, according to the values you give above…

A negative result is a value less than 20 (<20)

An equivocal result is any value between 20.1 - 24.9

A positive results is a value greater than 25 (>25)

Your result value is given as 2.15 - that’s less than 20 (<20) - so your antibody test is negative. (Is it an IF antibody test - see below)?

Tests results and the reference ranges are given in the same units - but there are different units that can be used - these can be lab, equipment (and sometimes country) dependent. But the test result is always given in the same unit as the test reference range - whatever measurement scale is used (hope that makes sense 🤔).

Bit confused by your Gp saying that he hasn’t tested IF yet - since the test for PA is the IF test.

If the test above was done by your GP (and not a private company) it may be that he has tested parietal cell antibodies - this used to be used as one of the antibody tests for PA but it is no longer recommended because it tends to give too many false positives (not all GP's know this). Is it possible he did these antibodies rather than IF antibodies? Since he says he hasn’t tested IF yet, this may be likely.

Think you need to ask what’s been tested - pariatel cell antibodies OR intrinsic factor. Whatever the test was, it’s negative.

But… about the IF test - 40%-60% of those with PA test negative for IF antibodies so a negative test cannot rule out PA. However, the test is very specific so a positive result is 95% certainty for PA.

Another thing to consider is whether your hypothyroidism is well controlled (the symptoms of B12 deficiency overlap significantly with those of hypothyroidism. The thyroid U.K. forum here on HU can help with all things thyroid. Here’s a link to that forum:

healthunlocked.com/thyroiduk

Also - worth noting that there are many causes of B12 deficiency, not just PA - although PA is the most common cause it’s worth considering and ruling out others - especially if your hypothyroidism is well controlled and you have unexplained symptoms.

Good luck with your GP.

[hani0902 in reply to Foggyme]

Thanks so much for your reply!

I understand the symbolism, my main thought was about the numbers and units as I can't find anything online that is similar to them. As far as I'm aware, the reference ranges are in AU/mL which is what was confusing me as this doesn't seem to make much sense to me.

It was also definitely an intrinsic factor antibody test as it says this on the lab results. I was also confused that there were units and not just a positive or negative. The GP also confused me... my speculation is that the tests aren't very conclusive for the antibodies and he's not telling me to avoid getting my hopes up about being negative? But that still doesn't make too much sense to me...

I also had my relevent thyroid labs and they came back completely fine as this was my original suspicion as to why I was feeling so poorly, the B12 and folate deficiency were found through this concern.

As far as other causes go, I'm absolutely not ruling anything out, of course. However, both of my mum's aunties were diagnosed with PA and my mum and sister have had struggles with B12 deficiencies. Further to this, my mum is diagnosed with MS and Hughe's. Autoimmune disease runs in the family which is why I am leaning towards PA.

Hopefully this adds a bit more relevant detail as to why I am concerned/confused.

Thanks again for your reply, I really appreciate it!

[Foggyme Administrator]

Yes, unfortunately there isn’t a gold standard test for PA or for B12 deficiency. Some have B12 deficiency and never get to the cause. If IF is negative (as yours is), if all other causes have been rules out, then the diagnosis should be antibody negative PA (ABNegPA). It’s in the diagnostic guidelines published by the BSH, but most GP's don’t read them and have never heard of ABNegPA.

Assuming your GP is treating your B12 deficiency? If symptoms improve, then that’s a win - and treatment (or a therapeutic trial of B12) is often the best way to determine if that’s the problem.

Thinking about autoimmune disease running in the family - hope you GP has done an antibody panel to see if any other antibodies are raised? There's a lot of overlap between the symptoms of B12 deficiency and the symptoms of a potential underlying autoimmune disease (and there are many of those).

There is autoimmune disease in my fa ily too. I was diagnosed with B12 deficiency (IF negative) and then went on a few years later to be diagnosed with Lupus (which I was told I'd had for many years - based on medical history) and just recently I've also been diagnosed psoriatic arthritis - another one to join the autoimmune party).

So… keep on with the B12 injections and if symptoms persist well worth investigating the possibility of other underlying autoimmune conditions.

It’s also worth saying that where B12 deficiency is concerned, being able to continue treatment (if it’s working) is the important thing - many never find out the cause and if and when every potential cause is ruled out, GP's rarely say ah ha, then it must be ABNegPA, because that’s what it is when it’s the only thing left. And that’s a shame because sometimes just getting a diagnosis is so reassuring for those who have suffered health problems - sometimes for many years!

So…here's a thought…you know from the above results that your GP is going to say you don’t have PA. Keeping in mind that 40-60% with PA test negative for IF ask your GP if he thinks you have antibody negative PA - see what they say.

Here's a link to the BSH guidelines - there's a diagnostic flow chart (about 8 pages in) that leads to and flags ABNegPA diagnosis - you could print that and pop it under their nose.

onlinelibrary.wiley.com/doi... in Haematology (BSH) Guidelines: Treatment of Cobalamin and Folate Disorders)

And just a last note - if you have a proven B12 deficiency (and it sounds like you have) your GP should be treating that - irrespective of whether they can easily identify the cause). With a intensive regimen of injections (every other day until no further improvement (for some, sometimes many months/years) - if you have neurological symptoms.

Anyway, good luck with it all. And it the B12 injections are working and you become symptom free - hurrah for that and you won’t have to worry or look any further.