Parietal Cell Antibody test refused by GP

[Needleandthread44]

I posted a few weeks back about my Dad who I suspect has b12 absorption problems either as a result of low stomach acid or PA.

He tested negative for IF antibodies so zi asked a GP at his surgery if they would test for Parietal Cell antibodies. She didn't seem to know what I was talking about?! Said they don't test for those. What is everyone else's experience, were they able to get tested through their GP? His docs are refusing intramuscular injections so he was having to pay privately.

[Gambit62 Administrator]

The WHO recommends not using GPCA testing as the test results in a high rate of false positives.

[Needleandthread44 in reply to Gambit62]

Oh I hadn't heard this. Thanks for replying

[jade_s in reply to Gambit62]

Do you have the report name or a link? I couldn't find anything through google or on the WHO's documents database. Lots of anemia & b12 docs but nothing about antibody testing in PA. Thanks!

Interesting because GPCA is frequently used both in practice and research papers. Most recent figures I saw as false positive was around 10% if i remember correctly. It's very frequently mentioned in papers I've recently read about autoimmune gastritis. In several they even suggest it's not even FPs per se because they see some go on to develop PA/AIG later. I'll have to dig through my papers when i have some time (battling covid at the moment so i've been quiet on here).

[Hidden in reply to jade_s]

Oh jade ... not dealing with covid as well !!Hope you have a speedy recovery.

[jade_s in reply to Hidden]

Thanks Sallyann!! 😊😘 It hasn't been too bad, as I already got omicron in january and had it fairly bad then. Now it's just like a bad cold though today my sinuses felt like they were going to explode 😳 Others in the family getting it for the first time have been floored ny it, despite being vaxxed and boosted. Interesting my nerves went crazy a few days so i added in extra shots & they helped. Crazy times! Take care x

[Rexz in reply to Gambit62]

Interesting...would be good to see that report. Everything I have read says 90% of those with PA test positive for PCAB and IFAB has 50% of those with PA being positive or conversely a large false negative? Here in the US it is common to do both tests at the same time. but either of those needs to considered holistically with all the other tests and with symptoms for a true diagnosis.

[Gambit62 Administrator in reply to Rexz]

jade_s Rexz short of going back through a lot of very old posts I don't have a reference re WHO, however, this is what the BCSH guidance on cobalamin and folate disorders says about GPCA as a testGastric anti-parietal cell antibody

Gastric parietal cell (GPC) antibodies have a low specificity for the presence of pernicious anaemia as, despite being positive in 80% of pernicious anaemia subjects, they are also positive in 10% of normal individuals. Positive GPC antibodies may cause gastric acid achlorhydria and progression to pernicious anaemia may occur. However, a positive GPC antibody test is not definitive for pernicious anaemia (Khan et al, 2009).

The guidance can be found here

onlinelibrary.wiley.com/doi...

The reference in the above can be found here

pubmed.ncbi.nlm.nih.gov/193...

[jade_s in reply to Gambit62]

Thanks Gambit! This is in line with what I was remembering.

[Rexz in reply to Gambit62]

Thanks for those posts Gambit. Yes, they are all just tools to gather evidence to reach a diagnosis. One thing is that sensitivity of tests also depends on which test method is used...sciencedirect.com/science/a...

One thing to consider is that if you've a family history of PA is that PCAB will show up positive long (possibly decades) before any other symptoms show up. Just my own food, as I've not read anything that would substantiate it, but it could be possible that these could fall into the 10% of "normal" people that test positive for PCAB.

Good discussion...thanks, Rex

[jade_s in reply to Rexz]

Yes that's what the AIG papers I read were suggesting. I should go look them up right now!

[Rexz]

Maybe refer your GP to this just one of the NHS sites in UK stating that PCAB is a valid screening test for Pernicious Anemia. Of course as it states all other symptoms and testing should be considered.

thepathologycentre.org/test...

And another that states PCAB is valid test and IFAB should be used to confirm PA after PCAB positive test.

pubmed.ncbi.nlm.nih.gov/193...

In either case these are valid diagnostic tools. Also if both are negative other literature from sites like Mayo Clinic say that does not rule out a diagnosis of PA.

I am certainly no expert but rather just a layperson trying to find my own way through all this! 🙃

Best wishes, Rex