Here we go again!
It would appear that >90% of testosterones are measured on platforms
supplied by 4 or 5 multinational companies.These and, from the Clin Chem
article, can't do it very well.Nor can the others.
No one buys an automated immunoassay platform because they want to measure
testosterone (or oestradiol for that matter); the platform was probably
acquired to do TFTs, gonadotrophins, tumour markers and other large-volume
analytes, but because there happened to be an assay provided by the
manufacturer then every lab decided to throw their testosterones on the
platform as well. How many labs critically assessed the performance of the
assay before putting them on the analyser? Many, I suspect had little or no
experience of measuring testosterone in their own lab.
We here in Liverpool do 10,000 testosterones per annum and we do not use an
automated platform and we extract all our female samples.
For what it is worth our A score is constantly <100 and we recover 90% of
NEQAS added testosterone.
Lack of precision and the very tight reference intervals probably prevents
assays being able to pick up subtle differences in concentration that might
reflect minor pathology. However if a woman shows signs of androgenisation
and serious pathology is ruled out then it matters little to her what the
testosterone-total, free or bioavaiable-or FAI or SHBG is, she wants
treatment. If we can ascribe the source of the XS androgen to one
particular organ then well and good-that might affect the treatment, but we
cannot do that by measuring testosterone except perhaps post selective
suppression tests.
I still believe that there is merit in measuring SHBG on borderline cases
in both males and females and calculating the free testosterone
concentration.
I have examples of normal youngish men with marginally low total
testostrerone (normal pituitary function) but very low SHBG and perfectly
normal calculated free testosterone and/or measured bioavailable
testosterone. I don't think they should be classified as hypogonadal as
they would be by measuring only a total testosterone (even in the early
morning!).
As long as manufacturers of automated immunoassay analysers tell the
jobbing biochemist that they can measure testosterone satisfactorily on the
platform and the jobbing biochemist believes them then we will make little
progress.
Michael J. Diver
Senior Lecturer
--On 28 July 2003 14:10 +0100 JG MIDDLE <[log in to unmask]> wrote:
> Listmembers who have agonised over which testosterone assay to use in
> women should be aware that a random number generator may be just as
> useful!
>
> The latest edition of Clinical Chemistry includes an article describing a
> major comparison study of commercial immunoassays with ID-GCMS (the
> reference method), and an Editorial deploring the current
> state-of-the-art of testosterone assays.
>
> Go here for links
> http://www.ukneqas.org.uk/saf01.htm
>
> To those who have followed the UK NEQAS ID-GCMS exercises over the years
> (you can download a pdf of the latest one for testosterone from the SAF
> link), these findings will come as no surprise.
>
> A major collaborative effort between laboratory, clinical and industry
> personnel is needed to address this issue.
>
> Useful discussions were had at the UK NEQAS SAF meeting last December;
> more concerted action is needed now.
>
> Jonathan Middle
>
>
>
> UK NEQAS Birmingham
> tel 0121 414 7300, fax 0121 414 1179
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> NEQAS Birmingham, the UK NEQAS Organisation, the University Hospital
> Birmingham NHS Trust or University of Birmingham.
>
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