Antibody interference in thyroid assays: a potential for clinical misinformation

[editfmrt]

I know this study is from 1998 so may be old information - apologies if this has been posted before. There are more up to date articles about this and from the uk but this one had much more information:

clinchem.org/content/44/3/4...

I remember reading that the TSH test has been improved so am not sure if that is related to this. Does anyone know? If this is still current, then it's another factor against the reliability of thyroid function tests and a strong argument for antibody testing.

[tegz]

I've seen more recent reports on ABs [mouse? etc] affecting thyroid assays- so don't think the problems gone away.

Just getting the 'basic' tests would be a plus for many!

I paid to get TPOABs done and they were OK, thankfully.

[I know that's not a totally clear slate for me- but that's life!]

[editfmrt in reply to tegz]

Yes basic tests would be a start (if you can get past the labs making all the decisions).

[helvella Administrator]

Indeed there have been improvements but even now there can be issues with some kits and macro-TSH (an anti-TSH antibody bound to a TSH molecule). I blogged fairly recently. (Or should that be "posted" now? )

I think FT4 can still suffer interference.

We also need to be aware/remember that there are all sorts of things going on. E.g. antibodies to T4 itself, and T3.

So any assay which could be affected by antibodies needs to be viewed with a suitable scepticism. But not being lab scientists, we find it very difficult to be sure of what can happen, in which tests, etc. Though I doubt we are much less aware than some endos.

Rod

[editfmrt in reply to helvella]

Ah I wondered thanks Rod. I was reading the SPECIALTY TRAINING CURRICULUM for Endocrinology & Diabetes Mellitus (Updated 2012) and in the thyroid section it says the first skill they need to attain is:

"Interpret thyroid function test results to diagnose and exclude thyroid disease and to recognise assay interferences".

jrcptb.org.uk/trainingandce...

What a joke when they won't take the tests in the first place! Note how many pages there are for diabetes compared to thyroid!

I'm busy composing a letter to the hospital endocrinology department that my sister is being treated by and making sure I get my facts right - that's why I asked the question to make sure I get my facts right.

Thanks again for your input.

[helvella Administrator in reply to editfmrt]

Also this brand new paper re interference with thyroglobulin assay.

Serum thyroglobulin (Tg) is useful for monitoring patients with differentiated thyroid cancer (DTC) but is limited by interference from anti-Tg antibodies (TgAb). We determined Tg assay discordance between a radioimmunoassay (RIA) and one of two immunometric assays (IMA) in DTC patients over a 9-year period to gauge assay performance against evidence of recurrent/progressive DTC.

ncbi.nlm.nih.gov/pubmed/238...

Rod

[editfmrt]

Nope - link must be too long! Aaarh

jrcptb.org.uk/trainingandce... Endo and Diabetes Curriculum (AMENDMENTS AUG 2012).pdf

[helvella Administrator in reply to editfmrt]

I think it is not the length but that it contains a space character!

Try this:

tinyurl.com/TUK-HU-SpecTrain

Rod