I recently tested positive for intrinsic factor blocking antibody but the result of my parietal cell antibody test was negative. I’m curious if other members have had this same experience?
My doctors have suspected a PA diagnosis for several years. An IFA test about five years ago produced negative results.
I am curious to know why and how b-12 injections can produce false positive IFA results? I ran across a study that showed injections up to 48 hours could affect the test outcome. However, US labs recommend going without an injection for 48 hours to two weeks before having an IFA test.
Curious to learn more about this if anyone has knowledge? Thanks in advance!
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mcg-woo
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I think this one is open access sciencedirect.com/science/a...Comparison of different immunoassays for the detection of antibodies against Intrinsic Factor and Parietal Cells
Basically they are all highly robust and do not give false positives, at least these 5 common assays. The Euroimmun IIF was slightly prone to FPs.
Just an anecdote, I've had 3 or 4 IFAB tests - I keep forgetting the exact number - while injecting daily, and have not once gotten a false positive. Which is annoying because I would totally play dumb and shove that FP result into the doc's face going see! see! I have PA! 😂
Anyway, I suspect the labs are just being careful with the 48h - 2 weeks statement. I suspect the older assays were more vulnerable. I would however try to respect that to whatever extent possible.
Was your positive IF test after an injection, and how long? They don't have much grounds to refuse it. It's totally possible to test positive and then later negative, or vice versa, it does not mean the positive was a false positive. It just means the antibodies were not active enough to measure on the negative test. Why don't docs realize the IFAB is not the end-all-be-all. I think we should all demand the Schilling test be brought back lol.
There is lady here and cannot for the life of me remember who, I'm sorry, but she and her whole family have PA, all IFAB positive but all GPC-AB negative. So yes it's totally possible and the literature doesn't contradict that, as far as I know.
Just bceause your GPCs are negative has no bearing on your PA diagnosis. If you need a reference to that, mcg-woo, let me know, and give me a few days, I'm sure it's there, I just have to find it back.
Jade-s, Thanks so much for the reply. The test was about 48 hours after an IM injection of hydroxo. I inject weekly. I have only been tested twice for IFAB—in 2016 (negative) and just in the past couple of weeks (positive).
I didn’t realize that I needed to wait a week before the test and wasn’t given that instruction. I only looked into it following the positive result. I don’t remember how long it had been since an injection the first time but I likely had a b12 serum test at the same time, so it was likely a couple of weeks , but not sure?
At one point during some previous b12 serum testing that I had done on my own, I went almost a month without an injection, felt awful and b 12 still showed up over 2000-unable to test that high. I am just not willing to go that long without an injection because if I do, I will pay the price and it will take me a long time to get back to feeling normal again.
I’m just going to do what Nackapan says and frame the positive IFAB result!
Lol Yes I'd frame it & say nothing to nobody 😂 it may very well be a true positive too...
I'm sorry hear you went through a bad period & hope things are better. I've been there done that too and it's crazy how long it takes to recover after even a short dip. Onwards & upwards
Thanks for the reply. I don’t have access to the full article, but here’s a link to a study indicating false positives were only observed in the first 24 hours of a b12 injection. Interesting..
Interesting, nice find! If your lab would share which assay they use, we might be able to find more specific details. If you have them time / interest of course.
This study is very dated—1984, so probably referencing an older test as Nackapan pointed out. The crazy thing is that if I went without injections and got a negative follow up test, it still would tell me nothing since it could be a false negative! After all, my first test was negative.
My gastro doctor has brought up the Schilling test more than once, saying it is the best test but no longer available, so IFAB is best that we have. There is just not enough interest in PA within the medical community and certainly not enough to dispel all the myths and untruths! Appreciate your input!
Jade-s, Yes! And you know the funny thing is that when my doctor asked if I wanted to run the tests, I almost turned him down due to my lack of faith in the IFAB test, but then I thought, what the heck—I’m doing bloodwork anyway. I had never had the parietal cell test either, so I thought maybe that test could give me an answer? Btw, I used the same lab for the positive test as the negative test
I was shocked when the nurse from the gastro doc’s office called me to tell me the results. She was concerned that I had not had a b-12 serum performed but I told her I didn’t need it because I was already on injections. She told me I probably only needed an injection every 2-3 months not weekly. Ha! I told her no that my GP and I had determined that weekly injections are what I need to stay symptom~free.
At least now I can be confident in knowing the cause of my b-12 deficiency which is helpful information for my children as they grow into adulthood.
I have heard that it can take several tests for antibodies to be detected in IFAB. I wonder if this is just happen chance based simply on the amount of antibodies circulating at the time of the test or if the amount of antibodies rise and fall based o the progression of the condition? As you said, they need to bring back the Schilling test!
Thanks again for the replies and I hope you are able to finally get your answer! Best of luck!
Thanks and best of luck to you, and your children too! I'd definitely keep an eye on symptoms and maybe even get some labs now to get a baseline.
injection every 2-3 months
😱 we'd all be dead!
I have heard that it can take several tests for antibodies to be detected in IFAB. I wonder if this is just happen chance based simply on the amount of antibodies circulating at the time of the test or if the amount of antibodies rise and fall based o the progression of the condition?
No idea! I have some theories but without further research we're left to speculate. We're having a parallel discussion about this on poor Holly's hijacked thread healthunlocked.com/pasoc/po... ... waiting for FlipperTD's reply
As for that last bit, "amount of antibodies rise and fall based o the progression of the condition" I personally highly doubt it's that, since so many of us seem to decline and yet test negative in the early days. If we truly had no antibodies in the early days, why are we getting so sick? The waxing/waning idea makes more sense in that context, and would also explain why some people test positive and then later negative.
Exactly! I’ve been without an injection for 3 months and I was the sickest I’ve ever been in my life! That is completely out of the question for me. I can’t imagine getting along every 2-3 months without an injection. When I see folks post here and say they haven’t had an injection for 3 months, I have to wonder how they are living like that? It was a miserable existence for me and I could not have survived without my kind doctor who gave me an injection instead of waiting to run labs.
Yes! I was worried about my kids a few years after my low b-12 was found because of anxiety, so I did have them tested. Their b-12 levels were around 800-900 at the time, but it is probably a good idea to keep an eye on it. I do supplement them with sublingual b12 from time to time just because of my experience and it’s not a bad idea for anyone. B-12 is water soluble after all—can’t get too much despite what some doctors think!
Thanks for entertaining my thoughts.
For all the Americans out there today, Happy Independence Day!
My heart also breaks for those on 3 monthly. For those who haven't or can't find their way to these forums. Luckily it's easier now than ever but so many are still victim to the whims of their doctors. Anyway... your kids are lucky to have you watching out for them
Hope you had a fun day and enjoy any fireworks later tonight! 🥳🎆
Appreciate the reply, Nackapan. I know, right! It only took almost 7 years to get a positive IFAB result. Even though it was expected, I was shocked when the result came back positive. I was relieved to finally know but disappointed as I’d hoped to not have a genetic component since I have two children and hope not to pass this along to them. The result will certainly help in the future. Though I’m able to access treatment through my physician now, I worry that when she retires, definitive proof wouldn’t exist and now I have it. I imagine I will still face the battle of finding a physician comfortable with weekly injections as a maintenance dose.
The gastro doc who ran the most recent positive test told me that he was concerned about me getting too much b12 with weekly injections and that the liver stored b12 for six months. I told him that b12 is water soluble so how could i get too much and the 6month liver storage scenario didn’t apply to me since I’d gone 3months without an injection and was so sick I was nearly out of my mind. Why don’t physicians know more about this!? Sheesh!
Nackapan, I don’t blame you. Too much of a gamble to take the test as it can be unpredictable. If it ain’t broke don’t fix it!
My GP told me after the first test which was negative, that the cause didn’t really matter because the treatment is the same—shots for life.
She also said that she really didn’t think it could be something else besides PA because of the severity of my symptoms. She saw me at my worst—three months without an injection. I must have seemed like a crazed lunatic. I certainly felt that way! Just feeling normal again these days with a weekly injection.
many tests use mass spectrometry - a process that allows them to measure the mass of various different metabolites. This means that test results can show false positives if there are other metabolites of similar mass in the sample - and presumably IFAB and B12 have similar mass.
Modern machines are sensitive enough to distinguish in samples 48 hours after an injection - but older bits of kit need the B12 levels to have fallen for 1-2 weeks before they are sensitive enough to distinguish - hence the false positives.
Gambit62, Ah-ha, makes sense. Thank you so much for the reply and valuable information! This puts my mind at ease and I can finally accept this for what it is. It has been a long journey to obtain proper treatment and to finally have a known cause.
My situation is a classic case with the timing of the onset in my forties and a slow, steady decline and all the classic symptoms. I had a misdiagnosis as well and difficulty reaching full remission until injecting weekly long term. I didn’t have loading doses, which delayed recovery. I am just grateful to be where I am today. Is still frustrating when doctor’s don’t understand the condition.
My mother is a type 1 diabetic with thyroid disease who doesn’t have PA and I wonder if somehow these genes aren’t connected? Her great grandmother died in an insane asylum and wonder if it was due to PA? Thanks again for the information and taking the time to reply. I think it is all very helpful to folks on the forum.
Or maybe your great grandmother was simply feisty, with a very impressive mouth.
Not being flippant with mental health or b12 deficiency causing issues but the more I watch older documentaries, well it seemed a lot of women were 'sent off' here & there.
I know I myself in a different age would be found in two places - a mental institution due to an overzealous man or my own mouth. Or I would be in jail. Pointe Finale.
I could not have coped with the pretense needed during those times.
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Wonderful on your test. My doctor was the same - no other reason but pernicious anemia, and documented without the test. Said same protocol no matter what.
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