Why don't you make or buy some steroid-free serum and make
dilutions of your lowest control? We still do extraction
testosterones on all our female samples because we are very
wary of fully automated testosterones at normal female
levels and with my admonishing hat on may I be so bold as
to say it deserves you right for changing to an automated
direct method from a perfectly good manual method. A quick
clance at NEQAS returns for female testosterones will soon
tell you what a devil of an assay it is and if you want to
delve into the history books you will observe that we are
no better at measuring testosterone nowadays than we were
when 'the purists' were using tritium labels, celite
columns, charcoal separation and scintillation counting.
As they say in the West of Ireland 'May good luck be with
you'
Mike D.
On Mon, 14 Aug 2000 16:25:34 +0100 "Grimes, Helen"
<[log in to unmask]> wrote:
> We currently use Centaur for male and female testosterone, but lack a
> normal/low female testosterone control level. The ligand controls supplied
> by Bayer only go as low as 3.6 nmol/l. We changed from DPC CAC testosterone
> to Centaur, and note an increase in the number of female elevated
> testosterone, i.e around 3.8-4.0 nmol/l, so either we missed females before,
> or have the wrong reference range (0.2-3.0) or we have interfering
> substances. Theorists will say we should confirm with extraction methods,
> but who is doing that nowadays? We know our CVS at the low end are about
> 15%, and so feel a lower control would be helpful. Has anyone located such a
> control?
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