Chance of False positive? : Do you think it is... - Thyroid UK

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Chance of False positive?

JennaShi profile image

Do you think it is possible to get a false positive on thyroid peroxidase antibodies test? I got results back and i had 1 (reference range = to or <1) for the thyroglobulin and >900 for the thyroid peroxidase antibodies. Thats pretty high.. is it possible to have a false positive or that this number is wrong?? Has anyone else had this a number or more or phlembotomist mis calculating?

9 Replies

I don't know how accurate the number but you probably have them. he explains them in this short video.

JennaShi profile image
JennaShi in reply to Heloise

Thank you Heloise, I will check it out :)

Think I've seen higher on here. Not sure what you mean about miscalculating. Phlebotomists draw the blood, they don't analyse it.

Were you given the diagnosis of Hashimoto's Autoimmune Thyroiditis? Have you been started on 50mcg Levothyroxine?

If you haven't had the following nutrients levels tested, you may wish to consider asking for them also:

Vitamin D





2nd reply


Have just had a quick look at your previous posts and see that you are already on 100mcg Levothyroxine plus some T3.

So you had your 3rd tests before they did your Antibodies? Strange?? Well, at least you know now!

With Hashimoto's, we start Hyper.

Have you had hyperthyroidism? If so how did you end up being hypo?

I was previously hyperthyroid and my doctor at the time recommended the Radio active iodine treatment. Still hyper after until for years ago, then it normalized and then do to some stress I went hypo this past Christmas.

I agree and thinks its odd how our bodies react. How do you help relieve your symptoms? Do you avoid dairy, sugar and gluten?

Oh ok, I didnt know that they didnt.

No I wasnt given the diagnosis of Hashimotos. I was formerly diagnosed with hypo and only tested for thyroglobulin.

I just recently decieded to order lab tests through a company seperate from my doctor and those were the results i recieved.

Yes I am actually taking 100 mcg of levo and 10 mcg of t3. I have been taking iron for iron deficiency anemia and have been tested previously for b12 and folate but came out normal. Will ask to test all of these.

Do you know if iron and selenium cause reactions against tpo as well? I have been eating brazil nuts because it seemed to have been helping.

Heloise profile image
Heloise in reply to JennaShi

These are the labs explained.

helvella profile image


The reference range being <1 is just because they have scaled the results. Like Concord flying at Mach 1 rather than 665 mph - same speed but easier number!

Some tests rely on the lab repeatedly diluting the sample - until the result is inside the range the test is designed for. But once the test has been positive for several dilutions it is usually stopped without carrying on and on. Hence the >900 result.

JennaShi profile image
JennaShi in reply to helvella

Ok thank you Heloise and Helvella!

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