Questionable validity of test results? - Thyroid UK

Thyroid UK

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Questionable validity of test results?

Fifteen profile image

Do thyroid tests have any use or even any validity? My results from the same blood draw but analysed by different laboratories have varied once again.

My story:

29/07/21 GP's NHS results:

TSH >0.01 (0.3 - 4.2)

FT3 4.4 (2.6-6.0)

FT4 14.2 (9.0 - 23.0)

29/07/21 Blue Horizon results:

TSH >0.005 (0.27 - 4.20) mU/L (New range and unit)

FT3 4.85 (3.1 - 6.8)

FT4 21.3 (12 - 22 pmolL)

When asked about the differing results, the response included:

You were is a hyperthyroid state at time of tests

Reported FT4 level is unreliable if you are taking T3

Whilst a lower TSH is the goal if one is taking T3, a very low level may imply overmedication regardless of FT3/FT4 levels

To continue: GP's NHS 21/01/22

TSH >0.01 (0.3 - 4.2)

FT3 4.8 (2.4 - 6.0)

FT4 15.7 (9.0 - 23.0)

T3 medication change by Endo from 15mcg to 20mcg T3, taken morning and early afternoon. Continuing 125 mcg T4 (I had recently decided to take 125mcg daily instead of 100/125mcg alternate days).

Latest - variation most confusing of all as officially both NHS testing

GP's NHS 11/04/22

TSH >0.01 (03 - 4-2)

FT3 5.4 (2.4 - 6.0)

FT4 14.3 (9.0 - 23.0)

Monitor Health - NHS Private 11/04/22

TSH > 0.01 (0.27 - 4.2)

FT3 6.3 (3.1 - 6.8)

FT4 21.8 (12.0 - 22.0)

With these variations in FT4 results from the same blood draw, do these results have any validity?

6 Replies

This post discusses the issue in depth . healthunlocked.com/thyroidu...

Especially with fT4 results done on different platforms ...i'm in the 'dubious' camp.

If you want to compare your fT4 this time to last time , then knowing what i know now , i'd use the same lab each time .

it' not so much a problem of any one lab being any more 'accurate' than the other , but the comparability between test platforms using different testing methods / with different ranges .. does seem to be a problem that is 'far from sorted' .

I think they do have validity because the ranges are different but looking at where you are in the ranges, say as a percentage, the results are pretty similar.

tattybogle profile image
tattybogle in reply to thyr01d

it' s the fT4 's that are the problem.

29/07/21 GP's NHS results:

FT4 14.2 (9.0 - 23.0) 37%

29/07/21 Blue Horizon results:

FT4 21.3 (12 - 22 ) 93%

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

GP's NHS 11/04/22

FT4 14.3 (9.0 - 23.0) 38%

Monitor Health - NHS Private 11/04/22

FT4 21.8 (12.0 - 22.0) 98%

Fifteen profile image
Fifteen in reply to thyr01d

Well spotted. Thank you. Just now have to decide whether to ask endo tomorrow for an increase in levothyroxine

Fifteen profile image
Fifteen in reply to thyr01d

Well spotted. Thank you.

Fifteen profile image
Fifteen in reply to thyr01d

Now to decide whether t ask the endo tomorrow for an increase in levothyroxine based on the NHS result

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