What TSH test is used affects diagnosis of hypothyroidism

[diogenes]

This paper demonstrates how using either the Abbott or the Roche TSH test affects a diagnosis of hypothyroidism. Amongst many other problems, this is a deeply unsatisfying state of affairs, as the differences are compounded with what the various users define as a TSH cutoff. The paper is behind a paywall, but I've put here the abstract which tells its own story:

Biochemical assessment of adequate levothyroxine replacement in primary hypothyroidism differs with different TSH assays: potential clinical implications

Tejas R Kalaria, Anna Sanders, Clare Ford, Harit Buch, Jonathan Samuel Fenn, Helen L Ashby, Pervaz Mohammed, Rousseau Mariano Gama

Journal of Clinical Pathology

dx.doi.org/10.1136/jclinpat...

Abstract

Aim

Thyroid stimulating hormone (TSH) assays provided by Abbott Laboratories and Roche Diagnostics are used by approximately 75% of laboratories in the UK. We assessed the potential impact of Abbott and Roche TSH assay differences on the biochemical assessment of levothyroxine replacement in primary hypothyroidism.

Method

Samples from 100 consecutive primary care patients (83 women, median age 64 years, IQR 51–73 years) with primary hypothyroidism on adequate levothyroxine based on an Abbott Architect TSH in the reference range were analysed for TSH on Roche cobas within 24 hours. The Abbott and Roche TSH results were compared. Over 1 year, TSH results from patients in primary care from the laboratories with Abbott and Roche methods were compared.

Results

The median (IQR) Roche TSH (2.5 (1.3–3.6) mIU/L) was 30%±10% higher (p<0.001) than Abbott TSH (1.9 (1.1–2.6) mIU/L). Although all Abbott TSH results were in the Abbott specific reference range, 14 patients (14%) had Roche TSH results above the Roche specific reference range. In the 1 year gather, Roche TSH (1.9 (1.3–2.9) mIU/L, n=103 932) results were higher (p<0.001) than Abbott TSH (1.5 (1.0–2.2) mIU/L, n=1 10 544) results. The TSH results were above their assay-specific upper reference limit in 10.7% of Roche results and 4.2% of Abbott results.

Conclusion

Biochemical assessment of levothyroxine replacement may be dependent on the type of TSH assay. Laboratorians and clinicians should be aware that the lack of harmonisation between TSH methods and their assay-specific reference ranges may potentially lead to different patient management decisions. We suggest lot verification in laboratories should include processes to identify cumulative drift in assay performance.

[Charlie-Farley]

Thank you diogenes

Interesting! 😊👍

A good study and perhaps perversely, I welcome the confusion. The less the Doctors can utterly rely on these tests and be made aware of that - the better chance (albeit still slim) they will actually engage brains and think about symptoms over lab results. I managed to argue to full replacement dose even though I was in range at every juncture, with sometimes strident debate as to the purpose of the range and where one might sit in it and feel well.

God help us! They already think everything can be explained and managed by lab results alone anyway. Any paper that casts doubt on this is worthy of mention.

No mention ever in these sorts of studies, if the patients have actually declared themselves as feeling well on their medication, or if this is a case of the patient being TOLD they are well as they are “within range”.

[Musicmonkey in reply to Charlie-Farley]

That was my immediate thought. More doubt cast on TSH as a diagnostic tool for thyroid status. One more nail in the coffin?

[Charlie-Farley in reply to Musicmonkey]

The trouble is the quality of the people using these tests, their ability to interpret data and to set it into the bigger picture and have a more holistic approach to peoples health.

I find that the doctors I have come in contact with in recent years do not seem to be able to interpret data, or have a joined up thought process, everything is so reductionist.

I remember a time when a family member was raging at the fact a receptionist had phoned up and given her in her blood results.

I can honestly say I see no difference in the delivery of results between a doctor and a receptionist now.

[Musicmonkey in reply to Charlie-Farley]

I also believe they are very guideline focused. It does make it extremely difficult for us patients who don't fit into a neat box (standard thyroid health problem = resolved by adequate Levothyroxine). If only...!

[Star13]

Thank you diogenes And if we didn’t have enough to put up with fighting the prejudice of TSH , now it seems we have inconsistent Labs!!

[Charlie-Farley in reply to Star13]

Hi Star13

A paper proving inconsistency in tests means we have some latitude to argue that the tests are not totally reliable and to push for our symptoms to be considered.

I personally think this is a good thing. They’re trying to ignore us anyway and tell us we are well (based on lab results) rather than asking us how we feel. This paper will take Doctors out of their comfort zone a little, something I applaud.

[Star13 in reply to Charlie-Farley]

Yes I agree. My Dr finally has put in writing that he doesn’t expect my TSH to change after 30 years of being deficient! He actually asked me how I felt and admitted I had no signs of over medication and told me to increase my T4 (I’m on combo). After years of fighting this it’s a huge relief. It’s just awful that we are forced to do it. I think the tide is slowly turning though but not fast enough for too many.

[Charlie-Farley in reply to Star13]

I agree,

I know people who do not belong to this forum (despite my enthusiastic feedback) who are not well on their medication, who KNOW they are not well on their medication and cannot bring themselves to have the ‘discussion’ and contradict the doctors assessment, “Your lab results are in range therefore you are well”.

There are still so many deferential patients about it’s heartbreaking. 😢

[tattybogle]

i'd really like to see a similar comparative test done for some of the fT4 assays commonly used . Mine is now done using [ 7.9 -14]

previous results from same lab on presumably different assay machine have had ranges of;

[13-26] 2005

[9.5-20] 2011

[8-18] 2014

[7.9-14] 2018 onwards.

I strongly suspect that my fT4 results using the [7.9-14] assay are coming out at a significantly higher % through / above range than they would using the previous [8-18] assay... but i can't prove it.

I agree , this study is very useful, as anything that casts doubt on the infallibility of TSH must surely be helpful in getting the medical fraternity to use their brains more than they currently do .

[Zephyrbear]

Seems to me that this just proves that doctors shouldn’t spend the entire consultation looking at test results on a computer screen mumbling “you’re normal” when an actual glance and a conversation with said patient would confirm the obvious fact they’re not! Sometimes all this technology has not always been an advance in treatment and in this case has been a considerable backwards move…