GGT was the subject of a recent audit carried out by the West Midlands labs.
At the audit meeting one of the participants indicated that the DVLC used a
cutoff of 1.5 times the upper reference limit quoted by the lab that carried
out the assay. This was a comment made during discussion and I have not seen
it verified by any other source.
If this is truly the approach taken by the DVLC then the advice to those
being tested would be to shop around. Reference limits identified in the
West Midlands survey were suitably diverse enough to enable different
conclusions to be drawn by the DVLC. Laboratories frequently derive
reference data from the literature, manufacturers pack inserts and only
partly verify them with limited local sudies. This can lead to errors of
interpretation when using data in the way described.
The use of evidence based/protocol driven medicine in coming years will
apply much more pressure to derive analytical systems that produce uniform
results and interpretation across geography. Application of protocols
nationally that use biochemical measurements to either initiate actions or
assess outcomes means that quality of care may be affected by inappropriate
action/inaction in a defined situation, or incorrect assessment of outcomes.
The use of a cut off for GGT, in the context described, highlights the type
of problem that could result. HbA1c would represent another good example.
Regards
Bill bartlett
> ----------
> From: Alison Jennings[SMTP:[log in to unmask]]
> Reply To: Alison Jennings
> Sent: 16 November 1998 08:29
> To: [log in to unmask]
> Subject: Gamma GT
>
> Although many labs try to dissuade doctors, particularly GPs, from
> the use of GGT as a marker of alcohol abuse, it would appear that
> the DVLA still puts reliance in this. Does anyone have any
> information about the DVLA guidelines about this, and has anyone
> spoken to them about this? We would appear to be giving out
> conflicting messages, if we do not advocate it for clinical use, but
> continue to perform it in response to requests from the DVLA
>
> Alison Jennings
>
> Alison Jennings
> Tel: 0113 392 2589
>
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