Comparison of method related reference intervals for thyroid hormones: studies from a prospective reference population

[helvella]

About all I can say about this is, what does "urgent" mean? Certainly hasn't happened in the many decades since diogenes did his test development. Yet every company and researcher involved has had the opportunity to at least try to go in the direction of standardisation.

O - and has anyone ever seen guidelines that properly refer to lab reference ranges rather than either the authors' own lab or some theoretical standardised ranges?

Ann Clin Biochem. 2017 Jan 1:4563217691549. doi: 10.1177/0004563217691549. [Epub ahead of print]

ANNALS EXPRESS: Comparison of method related reference intervals for thyroid hormones: studies from a prospective reference population and a literature review.

Barth JH1, Luvai A2, Jassam N3, Mbagaya W4, Kilpatrick ES5, Narayanan D2, Spoors S6.

Author information

1Leeds General Infirmary.

2Hull Royal Infirmary.

3Leeds Teaching Hospital Trust.

4Leeds Teaching Hospitals NHS Trust.

5Sidra Medical and Research Center.

6Doncaster and Bassetlaw Hospitals NHS Foundation Trust.

Abstract

Introduction Reference intervals are dependent on the reference population, the analytical methods and the way the data is handled statistically. Individual method related differences have been studied but the comparative differences in reference intervals have not.

METHODS:

We studied a reference population of healthy adult subjects and measured free thyroxine and TSH by the four most commonly used analytical platforms used in the UK. Subjects were excluded if they were >65 years or had positive thyroid peroxidase antibodies. We also performed a systematic literature review of thyroid hormone reference interval studies in non-pregnant adults.

Results 303 subjects were recruited and 42 excluded. The central 95th centile values for TSH (miu/L) were Abbott Architect (0.51-3.67); Beckman Unicel DxI 0.57-3.60); Roche Cobas (0.60-4.31) and Siemens Advia Centaur XP (0.63-4.29). The 95th centile values values for thyroxine (pmol/L) were Abbott Architect (10.6-15.5); Beckman Unicel DxI (7.9-13.0); Roche Cobas (12.5-19.6) and Siemens Advia Centaur XP (11.8-19.0). We identified 55 papers describing thyroid reference intervals in male and non-pregnant female adults. The values for upper and lower reference intervals by manufacturer varied but were not significantly different for TSH but were for thyroxine.

Discussion Our study demonstrates clearly that there are marked variations in the reference intervals for thyroid hormones between analytical platforms. There is an urgent need for standardisation of thyroid hormone assays to permit transferability of results. Until then, guidelines will need to reflect this method related difference.

PMID: 28081637

DOI: 10.1177/0004563217691549

ncbi.nlm.nih.gov/pubmed/280...

[Learner1]

They have hypothyroid people in their ranges!

Most US labs have changed upper TSH reference interval to 2.5-3.0, down from 4.5-5.0, as they realized the people above 2.5 were hypothyroid....

[diogenes Remembering]

Wow! Well whatever next! AND do you know that these four methods are decidedly not the best that could be used. Why? because the work to validate the methods has been superficially done. It's not enough just to look at a few hypos, hypers, euthyroids and pregnant samples. Nor to publish precision data - it's ACCURACY of measurement in all situations, however challenging, that counts, that is whether the number you get is the right one. In our pioneering studies developing FT4 and FT3 tests we examined EVERY category of challenging patient we could think of (common or rare), published not only the results but also the technical steps to produce and validate the assays for all to see. It has never been done by others since to that degree of concentration. What are the best? Elecsys and Vitros ECi for FT4 and FT3. But the managements there do not blow their trumpet on this as they ought, it isn't fashionable to bother about thyroid parameter measurements because "it's old hat". To me it's remarkable that after 36 years since the invention of convenient tests, papers like this can still be published.

[helvella Administrator in reply to diogenes]

I rather expected a response like that! Thank you so much.

[Hidden]

I do not want a TSH that lies somewhere, anywhere within ANY range, especially one that is certain to include people who have undiagnosed hypo- or hyperthyroidism.

I want my TSH to be the same as Usain Bolt, Moh Farrah or any other Athletics Olympic Gold Medal winner (excluding any Russians, of course!)

[humanbean]

The central 95th centile values for TSH (miu/L) were Abbott Architect (0.51-3.67); Beckman Unicel DxI 0.57-3.60)

As far as I recall, I have never seen an upper limit for a TSH reference range in the UK which was as low as these two. What does the NHS do when the top of the range is this low? Decide that would mean they have to treat too many people so they bump it up to something they consider more acceptable economically?