Joining this discussion late due to annual leave but we resorted to releasing this memo when the Trust moved from BD to Sarstedt tubes as we actually had no
idea what our referring labs were sending other than when a whole blood was sent in error. We can only make a recommendation and hope our “customers” on site or off it take the advice.
Slightly edited version of the data generated in house attached.
Regards, Fiona
From: Clinical biochemistry discussion
list [mailto:[log in to unmask]] On Behalf Of Adam Stretton
Sent: 18 August 2018 12:27
To: [log in to unmask]
Subject: Re: zinc analysis - are trace element free tubes required?
Dear Mailbase,
Just to add to the discussion if I may, there is significant evidence to support the use of specific tubes for trace element determination,
sufficient that relevant guidelines mandate their use. From CLSI Guideline C38-A - Control of Preanalytical Variation in Trace Element Determinations, 1st Edition, 1997:
‘However,
it is mandatory for any laboratory performing trace element determinations
to ensure that all collection devices, reagents and consumables used in collection, transportation, storage , or analysis will not contribute to the contamination of the specimen by the trace element of interest. No container or device, even if stated
to be suitable for trace-element analysis, should be used until evaluated’.
From the Tietz Textbook of Clinical Chemistry and Molecular Diagnostics, 6th Ed, 11th revision, 2016:
‘Trace metal-free tubes are commercially available and are essential for elements such as aluminium, Cr, Mn, and Zn.’
Many of the elements are present in the environment in much higher levels than found in patient specimens, or are used during
the manufacturing process. It is therefore difficult to control their levels in manufactured products. It would be prohibitively expensive/practically impossible to remove these elements from every in vitro diagnostic medical device, and would it even be
necessary? Manufacturing devices specifically controlled for the required elements allows us all to focus on what’s needed. It’s also useful to remember that blood collection involves a system, not just a tube, validation of the test process also needs to
include the collection device. Finally, preanalytical interferences can also raise background levels in the supernatant (e.g. haemolysis in zinc testing).
I have included some references below (some from this millennium!), in addition to the Guideline and Book listed above. If I
can be of any further help, please let me know.
Adam
References:
Bornhorst JA, Hunt JW, Urry FM, McMillin GA. Comparison of Sample Preservation Methods for Clinical Trace Element Analysis by
Inductively Coupled Plasma Mass Spectrometry. American Journal of Clinical Pathology. 2005;123(4):578-583. doi:10.1309/l241wuer8831glwb
Frank EL, Hughes MP, Bankson DD, Roberts WL.
Effects of anticoagulants and contemporary blood collection containers on aluminum, copper, and zinc results.
Clin Chem. 2001 Jun;47(6):1109-12.
Homsher R, Zak B.
Spectrophotometric investigation of sensitive complexing agents for the determination of zinc in serum.
Clin Chem. 1985 Aug;31(8):1310-3.
Taylor A. Detection and Monitoring of Disorders of Essential Trace Elements. Annals of Clinical Biochemistry: An international
journal of biochemistry and laboratory medicine. 1996;33(6):486-510. doi:10.1177/000456329603300603
Adam Stretton
Clinical Manager – UK&I
BD Life Sciences – Preanalytical Systems
1030 Eskdale Road
Winnersh Triangle
Wokingham
Berkshire
RG41 5TS
m:+44 (0)7795 237652
bd.com
From: Clinical biochemistry discussion
list <[log in to unmask]> On Behalf Of John
Sent: 16 August 2018 13:33
To: [log in to unmask]
Subject: Fwd: Re: zinc analysis - are trace element free tubes required?
I recall, in less austere times, the SAS Trace Metal labs would supply trace metal tubes free of charge to labs using the service. Also, they were very proactive in looking at potential sources of contamination which usually produced spuriously high results.
Many moons ago when I worked in Eastbourne I recall Guildford contacting me with a concern about ? spuriously low results as at that time none of the population seemed to be getting anything near the bottom of the reference interval. The candidate explanation
was that the water supply for that part of East Sussex was being drawn from aquaphores below the Severn Sisters chalk cliffs, so the water would have had to have passed through over 500 feet of chalk thus having most of the trace metals leeched out.
BW John
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Subject: |
Re: zinc analysis - are trace element free tubes required? |
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Date: |
Thu, 16 Aug 2018 11:55:28 +0000 |
|
From: |
GERRARD, Adam (BIRMINGHAM WOMEN'S AND CHILDREN'S NHS FOUNDATION TRUST)
<[log in to unmask]> |
|
Reply-To: |
GERRARD, Adam (BIRMINGHAM WOMEN'S AND CHILDREN'S NHS FOUNDATION TRUST)
<[log in to unmask]> |
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To: |
Unpublished experiments can only be considered to support expert opinion, which (whether we like it or not) is generally ranked as the lowest grade of evidence.
The internet seems to provide more forums for sharing opinions rather than facts, and as scientists we should be working to rebalance that by signposting peer-reviewed literature. If there are gaps in the literature and we have data to fill them, we should
publish it.
But that’s just my opinion.
Best regards,
Adam
Expert/moron/other*
*Delete as appropriate. If other, please state:
From: Clinical biochemistry discussion
list [mailto:[log in to unmask]]
On Behalf Of Nick Miller
Sent: 16 August 2018 10:34
To: [log in to unmask]
Subject: Re: zinc analysis - are trace element free tubes required?
Hi Trevor, good to hear from you! I just sent Mandy the following "off list" (I have to restrain myself in the face moronic comments):
"Well good luck Mandy - excuse my sarcasm, but I hope you get a grant, staff time, instrument time etc etc to show that using blood collection tubes that are contaminated with zinc
in various locations (particularly in the cap) changes the plasma zinc result. I have, of course, tried this out in various ways over the past 40 years and no, I didn't publish the results (along with my findings that the pyramids of Egypt were not built by
spacemen!)."
Cheers, Nick
On 16 August 2018 at 10:24, Trevor Walmsley <[log in to unmask]> wrote:
Greeting to you
The use of Trace Element evaquated collection tubes should be manditory for all trace element analysis. To do otherwise is inviting spurious results where deficiences
are missed and incidental findings lead to unneccessay investigations.
Regards
“We tortured the data until it confessed"
Trevor Walmsley
Emeritus Scientific Officer
Canterbury Health Labs
Christchurch
New Zealand
Phone: +64 3 364 0317
Mobile: + 64 27 4235 135
Fax:Phone: +64 3 364 0320
Internet:
www.hospitalscientists.org.nz/authorspub.php?key=639
Publications:
https://www.researchgate.net/profile/Trevor_Walmsley?ev=hdr_xprf
http://www.pubfacts.com/author/Trevor+Walmsley
all
From: Clinical biochemistry discussion list [mailto:[log in to unmask]]
On Behalf Of Nick Miller
Sent: Wednesday, 15 August 2018 10:13 p.m.
To: [log in to unmask]
Subject: Re: zinc analysis - are trace element free tubes required?
This is a policy based on convenience and economics rather than science! Nick Miller, London
On 15 August 2018 at 10:43, LAMB, Edmund (EAST KENT HOSPITALS UNIVERSITY NHS FOUNDATION TRUST) <[log in to unmask]>
wrote:
Totally agree we shouldn’t make recommendations without evidence. Surely any laboratories offering this service and insisting on a certain tube type will have verification data supporting their recommendations. Wouldn’t UKAS insist on such?
In east Kent we do not insist on a special tube and most of our samples are taken into gel-SSTs. Probably about 50% of our samples yield a result slightly below the reference range but probably of no clinical significance. It is very rare to see high results – in fact I can’t recall a high one. Are all of our slightly low results spuriously elevated by tube contamination i.e. actually deficient. This seems unlikely.
Insisting on a special tube type would require increased blood being taken and would probably result in more rejected samples.
Dr Edmund Lamb PhD FRCPath
Clinical Director of Pathology and Consultant Clinical Scientist (Biochemistry)
Tel: 01227-766877 extn 7224112
http://www.ekhuft.nhs.uk/patients-and-visitors/services/pathology/
follow us on Twitter @EKHUFTPathology
From: Clinical biochemistry discussion list [mailto:[log in to unmask]] On Behalf Of MCDONALD, Tim (ROYAL DEVON AND EXETER NHS FOUNDATION TRUST)
Sent: 15 August 2018 10:27
To: [log in to unmask]
Subject: Re: zinc analysis - are trace element free tubes required?
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
Barrack Road, Exeter, UK, EX2 5DW
t: Lab +44 (0)1392 402948
t: Medical School +44 (0)1392 408250
Website: www.exeterlaboratory.com
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
Error! Filename not specified.
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