A critical need for FT4 test standardisation

[diogenes]

This paper addresses a topic which I've long confronted - see my talk at the last TUK conference in Meriden. One cannot compare results from different labs if the methods of measurement used do not very closely agree with each other. This need has long been addressed by the Thienpont group but its implimentation by the various FT4 test manufacturers is slow or nonexistent, owing to the cost of recalibration and resubmission to regulatory authorities, with no discernible financial benefit. But if the field is to be more rationalised, this must occur, if necessary by regulatory force.

Free thyroxine measurement in clinical practice: how to optimize indications, analytical procedures, and interpretation criteria while waiting for global standardization

October 2022

Critical Reviews in Clinical Laboratory Sciences 

DOI: 10.1080/10408363.2022.2121960

Federica D'Aurizio, Jürgen Kratzsch. Damien Gruson, Luca Giovanella

[Musicmonkey]

Thank you diogenes . Here is the link:

tandfonline.com/doi/full/10...

[helvella Administrator]

About twenty years ago, the FDA required all USA levothyroxine products to re-apply for approval as if they were new medicines. (Due to their continual appearance in recalls and deep questions over switching products.)

Perhaps the approval authorities need to act, hopefully in concert, to require the companies to re-apply for approval?

(I know! A severe case of wishing thinking.)

[nellie237]

That was quite an interesting read. I didn't understand most of it, but I got the gist of it.

"Indeed, in a survey of 13 FT4 methods, more than 50% of the results in four of the methods did not meet the allowable inaccuracy criteria" Well, that's not really a surprise is it.

"Notably, patient-related factors such as changes in thyroid hormone receptor sensitivity, age, and sex add further complexity to the challenge of establishing specific RIs for patients treated with levothyroxine. In practice, it is preferable to monitor TSH levels in this population and to use FT4 measurement only in patients with central hypothyroidism." I have only 3 words to express my thoughts on this recommendation........Just F Off

[Charlie-Farley in reply to nellie237]

“In practice, it is preferable to monitor TSH levels in this population and to use FT4 measurement only in patients with central hypothyroidism."

the absurdity continuum 😱

Totally agree nellie237 - if I had been subjected to that practice I would have been grossly under medicated and very ill (still). Was bad enough being mismanaged at the start.

[diogenes Remembering in reply to Charlie-Farley]

Yes, whilst criticising tests for inconsistency, it was a fatally false step to take the conventional view that, because the tests were together as a class unsatisfactory, one should fall back on TSH. That's the outmoded view of present day thinking. The return of the art of diagnosis and treatment is not yet upon us.

[Charlie-Farley in reply to diogenes]

Sadly a dying art 🙄