Sulphite is not an uncommon finding in the urine of asthmatic patients:
its presence in this condition probably reflects inability to deal with
the breakdown products of sulphur metabolism or sensitivity to
sulphur itself - asthmatics are also, for example, very sensitive to
sulphur oxides in the air - rather than molybdenum deficiency or an
inherited disorder.
The Merck method is not sensitive enough to detect these small
amounts of sulphite, though it can be used to detect the quantities
of sulphite excreted in the inherited metabolic defects John Duley
mentions. I'm sure he's correct that an electrochemical method
would be the answer. Sulphite is also a bit more stable in urine
than you suggest, John, and can be further preserved by the
addition of ascorbic acid or boric acid.
In the mean time, sulphite in urine can be measured by the
decolorisation of para-rosaniline (basic fuschin), which is described
in outline by Vogel. The test can be made quantitative by running a
standard curve with aqueous sulphite solutions up to 20 mg/L; in
this form the test is sensitive enough to detect concentrations as
low as 2 mg/L.
Another problem with the Merck method, so far as I recall, is that it
also detects thiosulphate and is thus less specific than the para-
rosaniline method.
Hope this is of some assistance to anyone who wants to look at
urinary sulphite measurement.
Nick Miller
London
> Raised urinary sulphite is found in isolated sulphite
> oxidase deficiency and molybdenum cofactor deficiency
> (combine sulphite oxidase and xanthine oxidase
> deficiencies). These deficiencies are associated with
> severe neurological deficits (intractable fitting) and lens
> dislocation - no published evidence of respiratory problems.
>
> We use the Merck sulphite sticks routinely for the above,
> but the urine must be very fresh (ideally within 1-2
> hours), and the response on the sticks tends to be at the
> lower of the detection (colour change) scale, rather than.
> It is my guess that the levels you will be looking for, as
> you guessed, below the levels quantifiable on the stick -
> you will need an ?electrochemical method.
>
> - John Duley
> Purine Research Laboratory
> Guy's Hospital
> London SE1 9RT. GB
>
> --------------------------------------------------
>
> On Thu, 9 Nov 2000 09:13:52 -0000 Craig Webster
> <[log in to unmask]> wrote:
>
> > Sue,
> >
> > I've tried posting a few times but I think my email at home
> > is on the blink. Some paediatric labs may offer this
> > analysis as there is one (at least) in born error I think
> > that can give an elevated urine sulphite (Xanthine oxidase
> > deficiency). Another option is that Merck used to do a urine
> > dipstick test for this but it was formulated for water
> > analysis. Another possibility is (and again I'm on shaky
> > ground) is capillary electrophoresis as there are methods
> > for anion analysis in water.
> >
> > Hope this helps
> >
> > Craig Webster
> > Senior Clinical Biochemist
> > Nottingham City Hospital
> >
> > -----Original Message-----
> > From: acb-clin-chem-gen-request
> > [mailto:acb-clin-chem-gen-request] Sent: 06 November 2000
> > 17:45 To: [log in to unmask]
> > Subject: Urine Sulphite in asthmatic patients
> >
> >
> > A GP colleague, interested in alternative medicine,
> > recently enquired if I could get urine Sulphite done on an
> > asthmatic patient. He invited me to contact a Dr John
> > McLaren Howerd at Biolab Med Unit in London, which I
> > duly did. Dr McLaren Howerd has not published any of his
> > extensive studies (too busy providing a service to patients
> > to paraphrase him) but I did have a very interesting
> > conversation about it with him. I did a quick
> > internet search, which was a little sparse, and so now
> > wonder if any of my biochemistry colleagues could enlighten
> > me or point me to a good source of data. Is urine Sulphite
> > done by anyone (else) in the UK? Am I pitifully out of
> > date (I may well be)? HELPFUL replies welcomed ASAP!
> > Thanks. Dr Sue Walker, Salisbury.
>
> ------------------------------------------------------------------
>
>
[log in to unmask]
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|