Thriva's response to substantial difference in TSH result

[Bari77]

Hi all,

In my previous post I pointed out my Thriva TSH and FT4 blood test result was much higher than the NHS venous blood test done week before.

Thriva TSH 2.19 (0.27-4.20), NHS 0.76 (0.35-4.78)

Thriva FT4 14.4 (12-22), NHS 16.3 (10-20)

Here is their response to my email where I raised this.

We have previously spoken to our laboratory about the difference in TSH results. (I assume it happens regularly)

The lab we use explained that different laboratories, may use different testing platforms so the mean values of TSH can vary however they should be consistent and reproducible. They explained that the laboratories need to maintain the standards set out in ISO15189 if the lab is accredited. They suggested that check the status of the NHS laboratory, as many are struggling to get ISO15189. Certainly TSH levels can vary, so only two tests done together within a day of each other are comparable.

The laboratory also mentioned that the of day that the sample is taken can have a big impact but I can see that you're aware of this as you mentioned running the tests under the same conditions.

Our labs also suggested that it might be helpful to find out what testing platform the NHS lab uses to see how if it does run lower than the one they use. For reference your blood was tested by County Pathology on our behalf.

What would you infer from this? What does testing platform mean? I am not sure of validity and accuracy of Thriva test. However, I am having a free re-test so shall see.

[jimh111]

These results are consistent with your thyroid producing less hormone a week after the NHS test. Autoimmune hypothyroidism can cause erratic hormone levels.

I believe a testing platform refers to the machine and reagents they use to carry out the assay.

[Bari77 in reply to jimh111]

I don't believe I have autoimmune hypothyroidism- my antibodies est was negative. Unless I am in the 20% that apparently don't have increased antibodies.

[jimh111 in reply to Bari77]

I should have written that any thyroid disease can cause erratic release of thyroid hormone, the most common form is autoimmune. It's also possible you have TSH receptor antibodies which are usually associated with Graves', they occur in hypothyroidism also. There are other possibilities, you may have had variable absorption of your levothyroxine tablets especially if you switched brands recently. It's also possible the finger prick test didn't work properly. Even if it is verified there is still the possibility of user error or problems with heat in the post. I have noticed that most finger prick tests on the forum seem to correlate with NHS tests so I'm not slagging them off.

Edited: On reflection I don't think there was any problem with the finger prick assay. The TSH and fT4 figures are consistent, the Thriva results have a lower fT4 and higher TSH. This suggests your hormone levels changed between the two tests.

[Bari77 in reply to jimh111]

Thanks for this. How does one test for receptor antibodies?

[jimh111 in reply to Bari77]

Not really practical. They can assay TRAb which shows that there are Graves' antibodies but not whether they are blocking or stimulating, for that you need 'biological' assays which are only available in research. In any event if there are antibodies it just shows they could be affecting your thyroid, not whether they actually are and certainly not in a quantitave way. A diseased thyroid is erratic for a number of reasons, it doesn't really matter which reason as you can't do anything to correct it. If secretion is varying a lot and causing problems they can use 'block and replace', suppress your thyroid with carbimazole and replace with levothyroxine.

Your thyroid results are varying a bit but not much, I would just accept it and not worry about the fluctuation. It's quite normal. Blood tests are a rough and ready aid to diagnosis and treatment.

[Bari77 in reply to jimh111]

thanks. that's reassuring.

[Bari77]

Thanks. You see, that is fairly similar unlike my NHS and Thriva results. Let's see what my re-do Thriva test will show.