Which blood tests?

[missheid]

Can you please tell me which blood tests I should get to check for B12 deficiency, B12 absorption, and pernicious anemia? I'd like to take the list to my doc. Also, please tell me why each test is done. Thank you!

[fbirder]

A serum test for B12 will give an indication as to whether you have a B12 deficiency. However, many people who fall within the 'normal' range can still have symptoms.

Methylmalonic acid (MMA) is a biochemical used up in one of the processes mediated by B12. If there's not. Enough B12 getting into the cells then the levels of MMA in the blood will be raised. There are other possible causes of high MMA (like poor kidney function) but those can be eliminated if you did get a high result.

IMNSHO, one of the best tests for a B12 deficiency, that can be applied to people with relevant symptoms, is a trial of B12 injections. If the patient gets better after a course of injections then it's a fair bet that lack of B12 caused their symptoms. However, most doctors wouldn't agree.

If you are shown to have a deficiency then they can test for PA by looking in the blood for anti-IF (Intrinsic Factor) antibodies. However, the test gives false negatives in 50% of cases. So a positive means you almost certainly do have PA, but a negative doesn't mean that you don't have it.

[Steap]

What you mustn't do is take b12 before the test results are back and you have your diagnosis. Taking b12 makes the results look high and could set you back months.

Equally until you know your b12 is at a decent level or have started treatment to increase your levels be careful not to add folic acid to your regime as it is possible this could cause or worsen neurological complications.

I think I'm wearing both those tee shirts.

Folic acid and multivitamins in the absence of decent b12 levels can cause your body to use up the small amount of b12 you have left quickly and also mask some of the diagnostic features seen in a full blood count by correcting anaemia that would make alarm bells ring otherwise.

Best plan is to be tested on a healthy diet alone (with only prescribed medications)

[fbirder in reply to Steap]

Not quite...

Taking more folic acid doesn't use up what little B12 one might have faster.

There is little to no evidence that supplementing with sensible amounts of Folic acid can cause or exacerbate neurological problems. And plenty of evidence that low folate can cause such problems.

But it can, indeed, mask macrocyclic anaemia. And taking B12 supplements will screw up results for B12 and MMA. Anti-IF test isn't affected for more than a few days after B12 supplements (unless they're using a 25-year-old test).

[missheid]

Thank you for these great answers! I am sorry... I neglected to say I have already been diagnosed with B12 deficiency. I've been on twice-monthly B12 shots for 18 months, and feel fine. My levels are in the 700s-900s. But I wonder how much B12 I am actually absorbing.

Also, I have dueling diagnoses.

I am consistently negative for IF antibodies, but positive for parietal cell antibodies. Upper endoscopy revealed gastritis, and an atrophied-looking stomach lining, but biopsies are negative for atrophic gastritis. Also, my blood cells look good, not misshapen, but I am concerned that maybe I really do have PA. My endocrinologist believes we caught the B12 deficiency just in time, and that I'm subclinical PA, and believes I have autoimmune atrophic gastritis. I also have Hashimoto's, and a nodule on my thyroid, but no symptoms since I've been getting B12 shots! My gastroenterologist feels that I don't have PA or atrophic gastritis.

The good news is that my endo agrees I should see a hematologist if I want more info. I just want to know which tests I should be asking for. So I'll ask for a B12, an MMA, and what else?

Thanks again! So great to have input from you!

[fbirder in reply to missheid]

I'm not sure why you want more tests as you feel fine on your current treatment.

If your levels are up from 'diagnosed deficient' to 800 then you're obviously absorbing a reasonable amount.

The anti-IF test is notoriously unreliable, giving false-negatives half the time.

However, your combination of - low B12, positive for anti-GPC antibodies, gastric atrophy, and a positive reaction to B12 treatment - all indicate PA.

Your biopsy probably showed no sign of metaplasia, so you don't have autoimmune metaplastic gastric atrophy. That would suggest you've not had the problem for two long.

So I would be most happy to be in your situation - you're receiving treatment that enables you to feel fine. More than many of us can say.

[missheid in reply to fbirder]

I want more tests because I'd like a real diagnosis-- not two different diagnoses, one being yes you have subclinical PA, and the other being no you don't have any problems at all. So I'm going to see a hematologist. And I just want to be sure that the doc checks everything we're supposed to check.

[Steap]

They left me five years + with a b12 deficiency despite having a serum test on record of 146pg in 2012.

I'm really pleased they caught yours in time.

I'd read on here that taking the b12 co factors can increase the demand for b12 so if you have low reserves they end up being lower.

I'd guess that's why they say you always start the b12 before the folic acid.

That would seem to make sense.

[fbirder in reply to Steap]

Yes. Some nonsense found its way onto Wikipaedia saying that taking folic acid with low B12 could cause all the B12 in the body to be converted to methycobalamin, thus further depleting levels.

Tosh.

Wikipedia has now been edited to include correct information (with references).

The problem is that the misinformation has been cut 'n' pasted into loads of places on the Interwebs.

[missheid in reply to Steap]

My B12 was 166. And we just caught it by accident. We were looking for answers about why I wasn't sleeping. My endo threw in a B12 test--which normally I wouldn't get until my 70's here in the US. The level was low, and I started on daily B12 shots for 3 months, and I've been getting shots every other month since then.

I'm sorry to hear that it took a while for you to get help. Are you in the UK? Treatment seems to be different there.