Has anyone ever been unsure of their results and taken two tests around the same time eg. NHS and a private company ie. Blue Horizon to compare their results to see if there is much in the way of a difference in levels for accuracy purposes?
The reason I ask is via my GP/NHS it's never guaranteed that the blood nurse will arrive at a suitable time in the morning (as I have home visits) and also they are buggers for not testing T3, and usually it's an annual test but with my up and down results over the years and having Hashi's I need to test several times a year which is why I have, for a long time now, used Blue Horizon BUT I sometimes wonder about the accuracy of the results with a finger prick test and the sample being in the post 24-48hrs before it reaches the lab.
I have been looking at some old results and found a distinct difference in my T3 levels via the NHS compared to Blue Horizon results. Both results were me being on the same dose but the NHS test shows my T3 much higher in the range than has ever come back from Blue Horizon. My levels with them are usually in the low 3's or 4's although on both these sets my T4 and TSH look around the same, so maybe it's just ME?
Sept 2022 - Blue Horizon
TSH L 0.04 0.27 - 4.20 mU/L New range & unit
T4 Total 124.0 66 - 181 nmol/L
Free T4 18.3 12.0 - 22.0 pmol/L
Free T3 3.89 3.1 - 6.8 pmol/L New range
**Dec 2022** - NHS blood test
T4 18.9 (11.50-20.70)
T3 5.6 (3.50-6.50)
TSH 0.04 (0.55-4.78)
Written by
Jefner
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Yes, I’ve done both NHS (venous) and private (finger prick and venous) from various companies minutes after each other and there are often differences. Sometimes significant.
There is no exact right or wrong. Add to that, I expect all hormones fluctuate all the time. The important thing is to be consistent with your testing method and lab used.
Based on my experience, I would caution avoidance of being too close to the bottom or top of the ranges (if on levothyroxine only and still feeling rubbish, physically and/or mentally as under and over replaced symptoms overlap) confirmed with another test a couple of weeks after if possible.
There will be differences, even with the same lab. For some unknown reason, my GP ordered both TSH and Thyroid function test. So I have2 TSH values and blood was taken literally one after the other. They were both sent to the same lab and tested the same day they were taken as results were ready 26h after the blood was taken. One is 7.19, the other 7.5. It's the nature of the human body that not all blood is the same, plus test accuracy plays a part too
Finding this really interesting and super relevant to me at the moment. My NHS test never includes T3 they only do TSH and FT4 so neither result much help but it's what they class as 'Thyroid function test' My TSH result is similar to yours 0.02
Literally doing the private test this week because my GP won't entertain that TSH and FT4 are not indicators for changing dosage. Haven't seen him in over 4 years and he's never asked about symptoms - when I say 'asked' I haven't spoken to him all communication comes through the reception staff, so no opportunity to ask questions either.
So the diff in fT4 is quite big ..... but i'm not surprised as i've long suspected the lower /narrower range of [7.9-14] might give rather exaggerated %'s near the top end, when compared to the higher/ wider 12-22 ish ranges.
So while i can't say with certainty if im a tiny smidge over range .....or a fair bit over range What i can tell is that i clearly have 'plenty ' of fT4 sloshing around .
Since i learned about the complexities involved in testing, i no longer expect any fT4 / fT3 / TSH test to be totally comparable to another one:
even if taken at the same blood draw and taken straight to lab to remove the unknown factors of transport/ temp/ time in a post office van etc .........i would still expect to see differences between different test methods machines ... sometimes significant ones .... so you are best to look at several tests taken over time to get a broader picture of what is happening , and to look for trends. and if you want to directly compare 'has it gone up or down since last time ?' .. you really do need to use the same test method/ machine/ lab.
eg . i retested a couple of months later (same conditions) and got :
TSH 1.63 [0.24 -4.2] ........ fT4 22.2 [12 -22] ..........101% So based on all three results , it's clear enough to me that i have 'very high end' fT4
Due to all this potential for variation between test methods , I only look at fT4 / fT3 results in terms of rather broad categories:
well below range / around the bottom end of the range / middling / around the top end of the range / well over range.
and when i get differing %'s , rather than assuming one is 'right' and one is 'wrong' , i will assume the level is most likely to be somewhere between the two.
TSH tests are a bit less variable/ more comparable as those tests have been more standardised. but until endocrinologists show more interest in pushing the testing industry to make fT4 / fT3 tests much more comparable with each other , we are stuck with with the current rather shonky system of NHS labs using several different test machines/ ranges.
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