Intrinsic factor antibody test result - Pernicious Anaemi...

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Intrinsic factor antibody test result

jointpain profile image
5 Replies

Hi all those who can understand results and what they mean.

My Intrinsic factor antibody blood test result was 0.99 U/ml which was described as Normal - No Action The reference given was <1.20U/ml also a note saying method and reference change as of 05/03/15

At the time of the test I had been taking sublingual B12 which had raised my B12 up from 178 to 452 ng/L ref range 150-900ng/L

I can believe I do not have PA but cannot understand why my B12 had dropped to 178 which was tested a month after taking B12 for a month, so it may have been much lower?

Most of my classic B12 deficiency symptoms started a couple of years after having a very traumatic appendectomy when I wonder if a good part of my ileum may have been cut out as my gastric problems started then. As a side question is there any way of finding out for sure?

Thanks for any input.

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Gambit62 profile image
Gambit62Administrator

IFA is a good test for showing that you do have PA - it tends not to give false positives (unless done to close to supplementation).

However, it is a really bad test for showing that you don't have PA as it gives false negatives 40-60% of the time depending on the exact test method - so a negative is a long way from showing that you don't have PA.

if nitrous oxide was used as an anaesthetic during the surgery that may well have inactivated your stores of B12 - the body normally rebuilds them quite quickly but if you have an absorption problem you may not have been able to rebuild them - which would explain the symptoms starting at that point.

jointpain profile image
jointpain in reply toGambit62

Thank you Gambit62 I had the appendectomy in 1996 a long time ago! Since then I have been too regular a visitor to the doctors, in light of the possibility that the IFA test is wrong I wanted to know how close a call is it? Like, am I easily normal on the borderline normal it is the numbers I don't understand. I don't want to go back and say my result at 0.99 is too close to call and be told I am wrong and be labelled as a hypochondriac as I feel I was at the previous surgery I was registered at.

Gambit62 profile image
Gambit62Administrator in reply tojointpain

it isn't about where your test is in the range - the test just isn't that useful in ruling out PA - and it is more to do with the test method and the use and existence of other substances in your blood and the test process that can be confused with IFA which is why the limit isn't 0.

If you want to raise this with your GP then I'd suggest referring the to the BCSH guidelines on diagnosis and treatment of cobalamin and folate deficiencies which they can access through the BNF - this includes a discussion of the limitations of all of the tests used in diagnosing B12 deficiency - including IFA

It can also be accessed here

onlinelibrary.wiley.com/doi...

Anti-intrinsic factor antibody (anti-IFAB)

The finding of a low total serum cobalamin level may be further evaluated by testing for anti-IFAB. If positive, the test has a high positive predictive value (95%) for the presence of pernicious anaemia (Toh et al, 1997), with a concurrent low false positive rate (1–2%) i.e. a high specificity. It identifies those patients with a need for lifelong cobalamin replacement therapy. IFAB is positive in 40–60% of cases (Ungar et al, 1967), i.e., low sensitivity, and the finding of a negative IFAB assay does not therefore rule out pernicious anaemia (hereafter referred to as AbNegPA). In addition, the positivity rate increases with age (Davidson et al, 1989) and in certain racial groups [Latino-Americans and African-Americans; (Carmel, 1992)].

Sleepybunny profile image
Sleepybunny

Hi,

It's possible to have a negative or normal range result in IFA test and still have PA.

See UK b12 documents and book below.

BSH Cobalamin and Folate Guidelines

b-s-h.org.uk/guidelines/gui...

Flowchart from BSH Cobalamin and Folate Guidelines

stichtingb12tekort.nl/weten...

"What You Need to Know About Pernicious Anaemia and B12 Deficiency" by Martyn Hooper

Martyn Hooper is the chair of PAS (Pernicious Anaemia Society). Book is up to date with UK b12 guidelines.

B12 is absorbed in terminal part of ileum so damage to ileum may affect B12 absorption.

"As a side question is there any way of finding out for sure"

If you access your medical records from GP surgery and any hospital records there may be something relevant.

Access to Medical Records (England)

nhs.uk/NHSEngland/thenhs/re...

nhs.uk/chq/pages/1309.aspx?...

Nitrous Oxide

Did you have nitrous oxide during your operation? Nitrous Oxide can inactivate B12 in body.

gov.uk/drug-safety-update/n...

B12 books I found useful

"What You Need to Know About Pernicious Anaemia and B12 Deficiency" by Martyn Hooper

Martyn Hooper is the chair of PAS (Pernicious Anaemia Society). Book is up to date with UK b12 guidelines.

"Living with Pernicious Anaemia and Vitamin B12 Deficiency" by Martyn Hooper

Has several case studies.

"Could it Be B12?: An Epidemic of Misdiagnoses" by Sally Pacholok and JJ. Stuart (USA authors)

Very comprehensive with lots of case studies.

"cannot understand why my B12 had dropped to 178"

Risk factors for PA and b12 deficiency

pernicious-anaemia-society....

b12deficiency.info/what-are...

b12deficiency.info/who-is-a...

UK b12 websites

PAS (Pernicious Anaemia Society)

Based in Wales, UK.

pernicious-anaemia-society....

PAS tel no +44 (0)1656 769717 answerphone

B12 Deficiency Info website

b12deficiency.info/

B12d.org

b12d.org/

UK b12 documents

BSH Cobalamin and Folate Guidelines

b-s-h.org.uk/guidelines/gui...

Flowchart from BSH Cobalamin and Folate Guidelines

stichtingb12tekort.nl/weten...

BMJ B12 article

bmj.com/content/349/bmj.g5226

BNF

bnf.nice.org.uk/drug/hydrox...

NICE CKS

cks.nice.org.uk/anaemia-b12...

I am not medically trained.

jointpain profile image
jointpain

Thank you Sleepybunny a very comprehensive answer if ever I saw one!

As to "I am not medically trained" you seem well on the ball, not like any doctors I have seen in the past 22 years! Even though I recently changed surgeries the most recent doctor never knew of sublingual B12 or sprays! Which gives you some idea what I am up against. I will go back to them and maybe tell them what I want rather than play stupid, allowing them to fob me off with whatever is profitable for them. I will work my way through your reading matter as we are well and truly snowed in here in North Wales for the next few days. The drifts are as high as the hedges! So no way of getting out!

Thanks again

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