Intrinsic factor antibodies

[Hsss7]

Can someone explain this test to me please. I got a numerical result and reference range rather than positive or negative as is the usual explanation in just about every source i can find. (2.7 result 0-6 range) Surely if you have any antibodies it’s positive but having a range suggests they should be over a certain level to be positive.

Parietal antibodies were also requested but the result shows as n/a so I assume they failed to perform the test for some reason. (Nhs)

[fbirder]

The test will have some uncertainty, not least because the amount of antibody circulating is very small. It's like trying to listen to a very weak station on the radio, even if there is nothing broadcasting on that wavelength you'll still get some noise. The 0-6 range is what they expect from noise in that assay. A positive will normally give a result quite a bit higher than the top of the range.

Here's an image that shows what a typical assay might look like. They are trying to see if there's a peak at the correct position. In A there definitely isn't. In D there definitely is. But B and C are difficult. andyjconnelly.files.wordpre...

The GPC antibody test is no longer recommended, which is probably why it's not been done. Too many normal people give a positive result.

[Hsss7 in reply to fbirder]

Thanks. I’m aware that there can be false negatives but a positive is pretty much confirmatory. I’m just confused a bit by how antibodies can be present but classed as negative. It’s good to know a true positive is significantly higher than range in most cases.

The “noise” explanation helps me a little in that I’m now thinking it’s a bit of an inconclusive result due to interference rather than presences of antibodies. The lower the number the more likely negative and the higher edging towards positive.

[Gambit62 Administrator in reply to Hsss7]

the test has its limits. It works using mass spectrometry which means that it can confuse chemicals that have a similar or even the same mass as IF antibodies with IF antibodies. The limit in the test 6.0 recognises the likelihood of other chemicals being in the blood.

[wedgewood]

Just found some info online. Took a picture but I don’t know how to send it to you ! It said — relating to I.F.A. test results .

Less than 1.20 AU/ml ——- negative

1.21-1.52AU/ml —————-equivocal

Greater than 1.53 AU/ml—-positive

[Hsss7 in reply to wedgewood]

I saw that but the units Au don’t seem to convert to u/ml so didn’t explain much to me.

[wedgewood in reply to Hsss7]

Oh , right . You didn’t say that your results were in u/ml .

[Hsss7 in reply to wedgewood]

You’re right. sorry. I try to remember units but do sometimes forget and that does make things confusing. I do wish that everywhere would use standardised units. (the ranges don’t match either though so that was the only hint)

[fbirder in reply to Hsss7]

Au stands for ‘Arbitrary Units’. U stands for ‘units’.

The tests they use are called ELISA (Enzyme Linked ImmunoSorbent Assay) and they don’t give results in masses like ng.

[Hsss7 in reply to fbirder]

I’m just reiterating what’s on my results report and that’s u/ml. Perhaps different labs do it differently or perhaps someone has made an error. It’s what it says though.

[SunnyWorld in reply to wedgewood]

What reference range are those based on wedgewood

[Sleepybunny]

HI.

Hope your doctor knows that it's still possible to have PA even if IFA result is negative or within normal range.

stichtingb12tekort.nl/weten...

[Hsss7 in reply to Sleepybunny]

It’s impossible to see the same dr twice as it’s all locums. Neither the first one who refused b12 supplements at 159 nor the One I asked recently about it falling post my supplements from 818 to 400 in 6 months think there’s any problem. None have had anything to say about the IFA other than it’s normal.