It is not simply the container into which the sample is collected that
matters. As Barry points out samples for zinc need to be separated promptly.
So into the equation comes secondary tube, transfer pipette, the laboratory
conditions and the laboratories protocol for separating samples.
I M House
Trace Element Laboratory
Medical Toxicology Unit
Guy's and St Thomas NHS Trust
Avonley Road
London
SE14 5ER
Tel 020 7771 5372
Fax 020 7771 5373
-----Original Message-----
From: Sampson, Barry [mailto:[log in to unmask]]
Sent: 23 August 2004 15:21
To: [log in to unmask]
Subject: Re: Trace element containers
There is no question that vacutainers other than the 'trace element'
designated tubes must always be rejected for zinc (and aluminium).
These tubes will invariably give a variable level of contamination. I
have never seen any contamination with copper or selenium. As more of
the trace element specialist labs are now using ICPMS and capable of
measuring all elements on all samples it is more prudent to be rigorous
and only accept trace element tubes for any element.
A further point is how long a sample takes to arrive in the lab from a
GP surgery. I showed many years ago that even after 2-3 hours at room
temperature there is a significant rise in zinc concentrations, so
ideally all samples should be separated as soon as possible.
Barry
Barry Sampson
Principal Biochemist and Honorary Lecturer
Trace Element Laboratory
Clinical Chemistry
Charing Cross Hospital & Imperial College School of Medicine London W6
8RF UK
Phone +44-020-8383 3644
Fax +44-020-8846-7007
[log in to unmask]
-----Original Message-----
From: Clinical biochemistry discussion list
[mailto:[log in to unmask]] On Behalf Of Eric Kilpatrick
Sent: Monday, August 23, 2004 2:47 PM
To: [log in to unmask]
Subject: Trace element containers
Dear all
We are wondering whether to reject trace element samples from GPs and
outpatients which have not been collected into trace element tubes
(vacutainers here). When looking up Assayfinder there seems to be quite
a
large diversity of opinion about what sample is suitable. For example,
some
labs only accept trace element containers for Zn while others are more
laissez faire. Some would reject SST tubes for Cu, while others not.
Most
seem to accept anything for Se.
On speaking to the head Becton Dickinson chemist in the US, she tells me
they only rigourously test trace element vacutainers for contamination
(as
well as acid washing, etc) and make no claims for any other container.
Indeed, she thought it quite possible that contamination varied from
batch
to batch in any of their other containers. Since they do not test them
they
have no idea whether contamination would be clinically relevant.
My question is, what evidence have other trace element labs used in
basing
their sample container requirements? Do we need to reject samples
collected
into other containers or are we being needlessly strict to even consider
rejecting them?
Eric
Dr. Eric S. Kilpatrick
Consultant in Chemical Pathology
Department of Clinical Biochemistry
Hull Royal Infirmary
Anlaby Road
Hull HU3 2JZ
Tel 01482-607708
Fax 01482-607752
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