False Positive PA Test

[lownskater52]

Hey guys,

I took a PA test recently (Intrinsic Factor Antibody) and it came back positive. I'm always a little skeptical so I did some more research. I ended up finding the information below from Quest who is the lab that did my test. I had been getting 3 b12 injections per week when I got the tests. I believe I got a false positive test. I'm going to take another test in a couple of weeks once I give the b12 shots a break and see what the test says.

"The IFAB test is a competitive binding immunoassay employing an antibody that is specific to the B12 binding site on intrinsic factor. A high vitamin B12 concentration in the patient’s serum may interfere with the assay and cause a false-positive result. Thus, a patient receiving a vitamin B12 injection 1 to 2 weeks prior to testing may have a false-positive IFAB result. Conversely, a patient with a previously negative IFAB result may have a positive result on a subsequent test if the 2nd sample was collected within 1 to 2 weeks of a vitamin B12 injection. Therefore, we recommend waiting at least 1 week after vitamin B12 injection to collect samples for IFAB testing."

[fbirder]

How up to date is that info?

It refers to a radioimmunoassay test that was superseded by an ELISA test over 10 years ago. But I wouldn't be surprised some labs still used to old unreliable RIA.

[lownskater52 in reply to fbirder]

I just pulled it off their website for the test I got. Should be up to date so they must be using the old version.

[Andrianna in reply to lownskater52]

Maybe we should email/call Quest Diagnostics and ask if they are using ELISA or radioimmunoassay test.

[Andrianna]

Hi lownskater52

I had the same exact question. My IF antibodies test came back as positive while i was taking a lot of B12 shots! I sent a screenshot to my doctor from the Quest Diagnostic website. The same exact spot that you found. And my doctor's response was, "It would not give a false positive test but a false negative test so this is real "

I want to retest as well. But so far - I haven't been able to wait that long without a b12 shot.

My gut feeling is that I have Intrinsic Factor antibodies based on my reaction to taking folic acid vitamins and based on the fact that my b12 serum levels were within the middle of the range.

[Nackapan in reply to Andrianna]

What was your reaction to taking folic acid? Thsnks

[Andrianna in reply to Nackapan]

Folic acid made my neurological symptoms of b12 deficiency blow up. I have no idea why.

Fbirder is probably right in that IF antibodies probably don't cause a bad reaction to folic acid. The issue is that you are NOT supposed to take folic acid if you are b12 deficient. I will create a new post and post a photo showing what my folic acid vitamin warnings say.

[AirAl]

My doc (actually a knowledgeable nurse practitioner) had me not inject for a month before testing IF B12 and Folate. I'm waiting for the IF #, but my B12 was high normal 5 weeks after not injecting. I'm wondering if my B12 is still descending (was very high 5 weeks ago due to deliberate generous injecting). My NP also had me stop using alcohol prior to the retest. I'm really curious about the IF #, maybe Monday. If I have IF, then my PA might be alcohol indeuced.

[lownskater52 in reply to AirAl]

Please keep us posted. I'd be very interested in the result

[AirAl in reply to lownskater52]

Will do!

[AirAl]

My IF AB test came back negative. That was after 5 weeks with no alcohol consumption. Does anyone know how long you have to be off b12 injections before testing for b12 to get a baseline reading. It showed at 778 pg/mL but Im worried it's still descending. Does alcohol impair or destroy IF?