IFAB testing guidelines per Mayo clinic laboratory website

[EllaNore]

I found this IFAB test guideline. I found a few things pretty interesting. This particular lab which is the lab that did my IFAB test says that you should be fasting for 8 hours before you take this test and you should not have had any B12 injections within 2 weeks prior to the test. Another interesting thing I found was near the end under clinical information, where it says that an IFAB test could be positive for people with rheumatoid arthritis or other autoimmune diseases such as thyroid disease could cause a positive IFAB test without having pernicious anemia. But could lead to PA in the future. I found this interesting. Since Lyme disease and rheumatoid arthritis often get confused by each other, could Lyme disease also give you a positive IFAB test? ( sorry Lyme is not an autoimmune disease but can cause them. It is a virus caused by a tick bite. I said that wrong. Sorry.) thanks Jillymo

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Logan Health Medical Center Laboratory Test Catalog

Logan Health Medical Center Laboratory Test Catalog

powered by Mayo Clinic Laboratories

Test Code IFAB

Intrinsic Factor Blocking Antibody, Serum

Additional Codes

Mayo Test ID

IFBA

Reporting Name

Intrinsic Factor Blocking Ab, S

Useful For

Confirming the diagnosis of pernicious Anemia

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Serum

Ordering Guidance

For a comprehensive workup of patients with suspected pernicious anemia, order ACASM / Pernicious Anemia Cascade, Serum, which initiates testing with measurement of vitamin B12. Depending of the vitamin B12 concentration, testing for intrinsic factor blocking antibody, gastrin, and methylmalonic acid may be added.

Specimen Required

Patient Preparation:

1. Patient should be fasting for 8 hours.

2. This test should not be performed on patients who have received a vitamin B12 injection or radiolabeled vitamin B12 injection within the previous 2 weeks.

Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Specimen Volume: 1 mL

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container

Serum Refrigerated (preferred) 14 days

Frozen 14 days

Special Instructions

Vitamin B12 Deficiency Evaluation

Reference Values

Negative

Day(s) Performed

Monday through Friday

Test Classification

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

86340

LOINC Code Information

Test ID Test Order Name Order LOINC Value

IFBA Intrinsic Factor Blocking Ab, S 31444-3

Result ID Test Result Name Result LOINC Value

IFBLA Intrinsic Factor Blocking Ab, S 31444-3

CMT31 Comment 48767-8

Clinical Information

The cobalamins, also referred to as vitamin B12, are a group of closely related enzymatic cofactors involved in the conversion of methylmalonyl-coenzyme A to succinyl-coenzyme A and in the synthesis of methionine from homocysteine. Vitamin B12 deficiency can lead to megaloblastic anemia and neurological deficits. The latter may exist without, or precede, anemia. Adequate replacement therapy will generally improve or cure cobalamin deficiency. Unfortunately, many other conditions, which require different interventions, can mimic the symptoms and signs of vitamin B12 deficiency. Moreover, even when cobalamin deficiency has been established, clinical improvement may require different dosages or routes of vitamin B12 replacement, depending on the underlying cause. In particular, patients with pernicious anemia (PA), possibly the most common type of cobalamin deficiency in developed countries, require either massive doses of oral vitamin B12 or parenteral replacement therapy. This is due to patients with PA having gastric mucosal atrophy, most likely caused by a destructive autoimmune process. This results in diminished or absent gastric acid, pepsin, and intrinsic factor (IF) production. Gastric acid and pepsin are required for liberation of cobalamin from binding proteins, while IF binds the free vitamin B12, carries it to receptors on the ileal mucosa, and facilitates its absorption. Most PA patients have autoantibodies against gastric parietal cells or IF, with the latter being very specific but only present in approximately 50% of cases. By contrast, parietal cell antibodies are found in approximately 90% of PA patients, but are also found in a significant proportion of patients with other autoimmune diseases and in approximately 2.5% (4th decade of life) to approximately 10% (8th decade of life) of healthy individuals.

Interpretation

The aim of the work-up of patients with suspected vitamin B12 deficiency is to first confirm the presence of deficiency and then to establish its most likely etiology.

Measurement of serum vitamin B12, either preceded or followed by serum methylmalonic acid measurement, is the first step in diagnosing pernicious anemia (PA). If these tests support deficiency, then intrinsic factor blocking antibody (IFBA) testing is indicated to confirm PA as the etiology. A positive IFBA test very strongly supports a diagnosis of PA. Since the diagnostic sensitivity of IFBA testing for PA is only around 50%, an indeterminate or negative IFBA test does not exclude the diagnosis of PA. In these patients, either PA or another etiology, such as malnutrition, may be present. Measurement of serum gastrin levels will help in these cases. In patients with PA, fasting serum gastrin is elevated to more than 200 pg/mL in an attempted compensatory response to the achlorhydria seen in this condition.

For a detailed overview of the optimal testing strategies in PA diagnosis, see ACASM / Pernicious Anemia Cascade, Serum and associated Vitamin B12 Deficiency Evaluation.

Cautions

Patients who have received a vitamin B12 injection or radiolabeled vitamin B12 injection within the previous 2 weeks may have high serum vitamin B12 levels, which can interfere with this assay leading to falsely elevated results.

Some patients with other autoimmune diseases may have positive intrinsic factor blocking antibody (IFBA) assays without suffering from pernicious anemia (PA). This is reported particularly in patients with autoimmune thyroid disease or type I diabetes mellitus. In the validation of this assay, 24 individuals with these autoimmune endocrine diseases were tested and all were IFBA negative. However, 5 of 15 of patients with rheumatoid arthritis were IFBA positive during the validation of this assay. The literature suggests such individuals may, in fact, be at risk of later development of PA.

Since this is a competitive binding assay, the risk of heterophile antibody interference is low. During validation, 24 human antimouse antibody positive specimens and 25 specimens with other heterophile antibodies were tested and all were IFBA negative. However, if the clinical picture does not agree with the IFBA test result, the laboratory should be consulted for advice.

Report Available

1 day to 3 days

Reject Due To

Gross hemolysis Reject

Gross lipemia OK

Method Name

Immunoenzymatic Assay

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[wedgewood]

Yes ,thanks for this EllaNore . It gave me something to think about . Thought ,in the first instance , my goodness , I have had Rheumatoid Arthritis for years , and tested positive ! Maybe I don’t have P.A. after all . But then, common sense stepped in — , I knew that I had had a very low B12 blood serum result before the IFAB test — well below range and also many symptoms of B12 deficiency . So I doubted no longer . .But it makes interesting reading . Normally I suppose Rheumatoid Arthritis/ thyroid patients don’t get an IFAB test if they don’t have a low B12 serum result , and don’t have B12 deficiency symptoms . Suppose it was done for research .But those 2 autoimmune conditions often accompany P.A. .

Thank you .EllaNore . You give us lots of good information. 👍

I

,

[EllaNore in reply to wedgewood]

I'm glad you found it useful Wedgewood. Yeah, I can't see them doing an IFAB for RA at all. so I don't know how they came up with that conclusion. But I thought it was interesting.

[Nackapan]

Goodness. A wonder if anyone has a clear diagnosis reading that.

Also awful injections being stopped if negative !

I'm confused now why the parietal cell antybody test isn't used to help with s diagnosis of PA if 90% of those tested positive have PA.

Seems like we need about 6

tests and a clinical diagnosis to be sure.

Amazing with all the technology now. .

So much better if done before injections start .

We all expel b12 at different rates .

I'm sure my leveks woukd still be very high after 2 weeks.

Yet a newbie to treatment much less 🤔

Are the private tests automatically reported to NHS G.p ?

[EllaNore in reply to Nackapan]

It's crazy nackapan, isn't it! I never expected all this confusion with a B12 diagnosis. I thought, finally an answer. BUT there are more questions than answers. 🤔

[Nackapan in reply to EllaNore]

Yes.

[Bellabab in reply to EllaNore]

Indeed and the problem is because the role of B12 is incredibly complex and we do not know anywhere near enough about it - yet. Also medics tend to forget this and look down their noses at the highly developed observational skills of medics in the nineteenth and twentieth centuries that lead to PA patients being fed pounds of raw liver - they then lived whereas previously they died. I like liver yet not that much and pleased to have the ability to inject EOD Cobalamin.

[EllaNore in reply to Bellabab]

Exactly Bellabab. They knew more back in 1800's about B12 doses than they do now. I don't know why it changed. Money and greed I suppose. Maybe they think they make more money off sick people in care facilities than they do off B12. They send you home with insulin no questions asked but not B12! SI is my lifesaver for sure.

[Bellabab in reply to EllaNore]

Not greed - its simply they have forgotten that medicine isn't just about scientific stuff - its still fundamentally based in forming a therapeutic relationship with the patient then observation and taking informed guesses.

[EllaNore in reply to Bellabab]

Right. That takes time and they have 15 minutes per patient. It's hard to get everything said in 15 minutes with complicated cases such as ours. And then you get a new doctor and have to start over. 😔

[MoKayD]

Interesting information. Thanks for sharing.

[B12life]

How ironic. Mayo clinic told me B12 was not my issue 2 years ago when I was bed ridden and then after leaving me hanging told me to tell them if I figured it out. I connected with another woman on the forum in the US that had the same experience. I've lost my faith in Mayo Clinic when it comes to these types of medical issues. Must be boring to them. "Leave me alone kid... Ya bother me.", is the feeling I got. It really was this forum that encouraged me to stick with B12 injections and ride it out until I got better.

I love their articles though. Ironically I found the many faces of cobalamine by mayo which is just a collection of cases from around the world and felt so wronged that the doc who told me to kiss off didn't even know about this article. I keep getting emails to donate to Mayo. Think on that one. Sorry for the rant but I got burned by them so badly and found out I wasn't the only one. I wish they would read and follow their own publications!

All in all, I love the information EllaNore!!! Thank you! And I do thank those at Mayo who do publish this kind of information. I have saved this thread so I can study up on the info here. Any and all info on this forum is enlightening and welcome in my book.

[Technoid in reply to B12life]

That's so disappointing B12life. I would have expected better from them given their reputation. Taking them down a notch in my book for sure...

[EllaNore in reply to B12life]

I'm sorry that happened B12life. I find that UC Davis and other renowned hospitals like that get a bit full of themselves. People think that the Mayo Clinic is going to be their savior. Same as UC Davis and Stanford University. But they are not. I just finished the article Many faces of cobalamin. It has a lot of highlighter pen on it now to give to my doctor. LOL Great article. Sorry they don't practice what they preach.

You can vent anytime. that is what we are here for. We all understand. Vent away.

Glad you found it helpful.

Good luck to you!

[B12life in reply to EllaNore]

hopefully my vent is caught by someone in the US on the same journey and it saves them the effort. This forum and all the people in it are my savior.

[EllaNore in reply to B12life]

They are my saviors too B12life! I can't thank everyone enough for getting me through this very confusing time in my life. I am glad you found this forum too. I live in Iowa and there is simply no one out here that knows about B12. However, I have never had better medical care than I am getting in Iowa compared to California. Even if they don't understand B12D, most are very compassionate. I would like to meet others with this near me. Maybe start a support group or something.