Is anyone able to give actual data to support this?
It seems everyone is in agreement, but what is the magnitude of the contamination? Those labs that offer to compare a blank tube from the same batch of the
main blood tube providers, what is the range of zinc levels seen?
BW
Tim
Timothy McDonald, PhD FRCPath
Consultant Clinical Scientist, Royal Devon and Exeter NHS Foundation Trust
& Clinical Associate Professor (NIHR Fellow), University of Exeter Medical School
Blood Sciences, Template A2,
Royal Devon and Exeter Hospital
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From: Clinical biochemistry discussion list [mailto:[log in to unmask]]
On Behalf Of Nick Miller
Sent: 15 August 2018 09:21
To: [log in to unmask]
Subject: Re: zinc analysis - are trace element free tubes required?
Ignore zinc results based on plasma prepared from samples that have not been collected in trace element free tubes! They will give the wrong (higher) results due to contamination from the tube, the gel (if present) and the rubber cap. The
whole history of zinc measurement in clinical chemistry, going back to Prasad in 1963, and the discovery of its essentiality in mammalian metabolism, depends on this. Prasad, of course, had to acid-wash his tubes and vessels. Also be very careful about how
you handle the samples for analysis. Nick Miller, London
On 14 August 2018 at 20:46, Gavin Murdock <[log in to unmask]> wrote:
Hi Mandy,
It would seem to me that the main reason for using a trace element tube is because BD actively monitor the levels of trace elements present in each batch before release and certify that, for zinc, no more than 40 μg/L will be present.
A standard SST tube is not monitored for the levels of trace elements in each batch so unless you were prepared to send an additional tube, from the same batch as used for the patient sample, for use as a blank then it would seem sensible
to use a trace element tube to minimise pre-analytical errors.
Regards,
Gavin Murdock
On Tue, 14 Aug 2018 at 16:18, PERRY, Mandy (ROYAL DEVON AND EXETER NHS FOUNDATION TRUST) <[log in to unmask]> wrote:
Dear mailbase
For zinc analysis, some laboratories insist on trace element free tubes, whereas other labs will accept serum from gel separator tubes.
Does anyone know of any data to demonstrate the requirement for use of trace element free tubes for zinc analysis, rather than serum gel tubes? Or any data to that shows that serum gel tubes give accurate zinc results?
I appreciate that it is widely reported that gel can cause falsely raised zinc results, but I am struggling to find any up to date data to support, or negate this.
With many thanks
Mandy
Mandy Perry, PhD FRCPath
Clinical Scientist, Royal Devon and Exeter NHS Foundation Trust
***Please note, my working days are Mon, Tue, Thurs and Fri***
Blood Sciences, Template A2,
Royal Devon and Exeter Hospital
Barrack Road, Exeter, UK, EX2 5DW
t: +44 (0)1392 402948
Website: www.exeterlaboratory.com
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