Thank you all for your input in this discussion. We do not measure zinc in our lab and I have learnt a lot from your responses.
I interpret that the consensus is that data is either anecdotal, or from 1960s/70s. I agree that it would be interesting to see published data for a comparison between trace element free tubes vs serum gel using
tubes from 2018 – if gel tubes do cause a problem then this should be very easily proved.
Thanks again
Mandy
From: HARRINGTON, Chris (ROYAL SURREY COUNTY HOSPITAL NHS FOUNDATION
TRUST)
Sent: 15 August 2018 09:34
To: [log in to unmask]; PERRY, Mandy (ROYAL DEVON AND EXETER NHS FOUNDATION TRUST)
Subject: Re: zinc analysis - are trace element free tubes required?
Dear Mandy
As previous respondents have said it's widely accepted that gel-tubes leach zinc resulting in a falsely raised value when measured by all available methods. We've definitely had this experience
in our lab over many years. I'm surprised that some labs accept gel-tubes for zinc and would caution against this.
However I thought I'd take a quick look at the literature and I too couldn't find any studies supporting this. I think this is probably because they were carried out back in the 60s and 70s and
the papers may not be so easily available on the internet.
We have done some related studies looking at leaching of zinc from rubber stopppers commonly used in freeze dried IQC materials. The graph below shows how zinc increases when in contact with the
rubber bung, whereas copper is stable.
In general I think the use of trace element free tubes should be encouraged, definitely for Al, Cr, Mn, Ni; it's a false economy not to use them as it leads to retesting and requires the supply
of a second tube, with associated testing costs and each batch may not have a consistent level of contamination, so blanking may be unreliable.
Kind regards
Chris
C. F. Harrington, BSc, MSc, PhD, FRSC
Principal Clinical Scientist
Royal Surrey County Hospital, Guildford
Deputy Director, SAS Trace Element Centre
Scheme Manager, UKNEQAS for Trace Elements and Guildford Peptide Hormones
Visiting Senior Research Fellow, University of Surrey
Direct Tel. 01483 689977
Fax. 01483 689979
email: [log in to unmask]
From: Clinical biochemistry discussion list <[log in to unmask]> on behalf of PERRY, Mandy (ROYAL DEVON AND EXETER NHS FOUNDATION TRUST) <[log in to unmask]>
Sent: 14 August 2018 16:18
To: [log in to unmask]
Subject: zinc analysis - are trace element free tubes required?
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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