I am sure there are as many best formula as there are
papers on the subject. The differences most probably
due to analytical variation of the 5 variables that
have to measured to do the calculation.have I think a
wide "osmolal gap" is at best, a guide that there may
be something amiss. But to use it these days is like
using a sledgehammer to crack a nut, when there
technologically and analyticallysimple methods to
measure alcohol.
David Brown
--- [log in to unmask] wrote: > See Ann Clin Biochem
(1997); 34: 692 - 693. Osypiw
> et al - What is the best formula for predicting
> Osmolar gap? for a useful discussion on the utility
> of various formulae.
>
> For more than 10 years we routinely performed the
> Osmolality test (freezing point) with every ethanol
> request from the Emergency Department, in addition
> to measuring ethanol. This was to detect the
> possible presence of non-ethanol "volatiles". We
> used the formula in Goldfrank's textbook of
> Toxicology (1.86Na + glucose +urea + 9)0.93.
> Empirically we set a cutoff of 15 for the "excess"
> gap (i.e. taking ethanol into account) and sent out
> the specimens to a reference lab for methanol,
> isopropanol etc, by GC if the gap exceed this
> cutoff.
>
> A year ago we conducted a review and audit of this
> practice and in consultation with the Emergency
> Department we gave up the Osmolar gap, with
> considerable savings.
>
> Mario D'Costa Ph.D. FCACB
> Director of Clinical Chemistry and Core Lab
> St. Joseph's Health Centre
> 30 The Queensway, Toronto
> On, Canada, M6R 1B5
> Tel: 416-530-6263
> Fax: 416-530-6559
> email: [log in to unmask]
>
>
>
> >>> <[log in to unmask]> 06/06/03 07:11AM >>>
> Many years ago, the following formula was published.
> I think it was in the
> Annals. Sorry, don't have the reference.
>
> 1.89 [Na] + 1.38 [K] + 1.03 [UREA] + 1.08
> [GLUCOSE] + 7.45
>
> John Thompson
> DPOWH
> Grimsby
> UK
>
> -----Original Message-----
> From: David Brown
> [SMTP:[log in to unmask]]
> Sent: 06 June 2003 11:53
> To: [log in to unmask]
> Subject: Use of osmolar gap to
> "estimate" blood alcohol
>
> I previously asked if there was a standard
> reference
> method for calculating osmolarityand of the
> 2 who gave
> replies (JK --2 X (Na + K) + Gluc +Urea and
> RGZ--(2 X
> Na)+Gluc +Urea) there would be an
> approximate
> difference of at least 2 X K, ie. 8 mmol.
> Any more formula users out there?. I used
> the Sigma
> blood alcohol method on our "acute lab
> analyser" for
> many years it was cheap and easy to run.
>
> David Brown
>
>
>
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