Can somebody explain these

[Sweenco]

I have Hashimoto and UAT my TSH is currently surpressed. I have all the symptoms of a b12 deficiency and my numbers have always been in the 200s(200-900) but doctor said all fine even tho I’m not. Anyway I was taking b12 tablets for a few months and stopped in November as I didn’t see any difference. First time I have had my active b12 tested, would me taking b12 supplements for a few months have interfered with this result, also because I have a folate deficiency would this mean my b12 isn’t getting used properly hence the horrible symptoms??

[fbirder]

Yes. And, yes.

Yes, assuming that you do not have an absorption problem taking the supplements would have raised your Active B12 levels.

Yes, a folate deficiency can cause symptoms similar to those of a B12 deficiency.

[Ryaan in reply to fbirder]

Whats the difference between active B12 test and a normal B12 test ?

[fbirder in reply to Ryaan]

B12 in the blood is carried around by two proteins, haptocorrin (HC) and transcobalamin (TC). Only the TC-B12 can enter the cells, so only TC-B12 (also called holotranscobalamin) is 'active'. The rest of the B12 (about 80% of the total B12 in the blood) is HC-B12.

Nobody is really certain why this system has evolved. The best reason I've read is that HC is a bit less discriminating. It will bind to real B12 but it will also bind to B12-like compounds (corrinoids). Doing this keeps these useless compounds from getting into the cells where they might block the functioning of real B12.

The serum test measures both TC-B12 and HC-B12. The Active test measures just TC-B12.

This shouldn't matter much. It's like counting sheep. You can count heads or you can count feet, and divide by four. Both methods will give you a fairly accurate result for the number of sheep in the field.

Assuming both methods are equally accurate and precise.

The people that sell the 'Active' test tell us that their assay is both more accurate and more precise and, more importantly, doesn't suffer interference with IF antibodies. The serum test can give falsely high results if there are lots of IF antibodies - as you might find in people with PA.

This is a presentation from the 2016 PAS conference. Not only does it explain it all very well. It also explains the problems of setting 'normal' ranges. It's a fine balance between sensitivity (catching people who are deficient) and specificity (not catching those who aren't).

youtu.be/l0hw1DyR57k(Not working as expected?)