From my 2004 poster
Discussion
The choice of sample type for TnI (and TnT) assays has been the subject of much discussion and there is still no consensus. Lithium heparin offers speed of separation and potential reduction of turnaround time but has been shown to interfere with troponin T and some troponin I assays. (refs 1 and 2). Serum samples do not suffer from heparin interference but the presence of microclots can cause erroneous results.
Speth and Seibold found that recentrifugation of serum samples to allow for incomplete clotting had no effect on results but they used Sarstedt serum separator tubes which performed better in the Leeds study
than Greiner and Becton Dickinson tubes.
Utweiler-Geiger et al (3) found that lithium heparin had no effect on Beckman Access TnI results. Beckman recommend lithium heparin samples should be used for the assay.
In the light of the results of the above study I would recommend that lithium heparin samples be used for the Access assay. If serum gel tubes are used TnI should be measured on an aliquot (not the primary tube) which should be recentrifuged just prior to the assay. The latter is the procedure used at Leeds infirmary (at least it was in 2004 when I left).
References
1 Speth M, Seibold K, Katz N Interaction between heparin and cardiac troponin T and troponin I from patients after coronary bypass surgery. Clin Biochem. 2002 Jul;35(5):355 – 62
2 Gerhardt et al Troponin T and I assays show decreased concentrations in heparin plasma compared with serum: lower recoveries in early rather than late phases of myocardial injury. Clin. Chem. 2000 Jun;46(6 Pt1):817-21
3 Utweiler-Geiger et al Muliticenter evaluation of an automated assay for troponin I. Clin. Chem 2002 (48):869-876
Mike Collins
BMS3
Biochemistry Automation
Norfolk & Norwich University Hospital
England
[log in to unmask]
http://www.nnuh.nhs.uk/
-----Original Message-----
From: Clinical biochemistry discussion list [mailto:[log in to unmask]] On Behalf Of Mohammad Al-Jubouri
Sent: 14 November 2013 13:43
To: [log in to unmask]
Subject: Re: Siemens troponin I ultra assay serum v plasma and ?flyers
Hi Steven,
This Australian study of falsely raised cardiac troponins has interestingly used Greiner tubes but didn't blame them for the falsely elevated results.
http://www.clinchem.org/content/57/5/710.full.pdf+html
BW
Mohammad
<b>Dr. M A Al-Jubouri, MB ChB, MSc, EurClinChem, FRCP Edin, FRCPath Consultant Chemical Pathologist</b>
--------------------------------------------
On Wed, 11/13/13, Steven John Mccann <[log in to unmask]> wrote:
Subject: Siemens troponin I ultra assay serum v plasma and ?flyers
To: [log in to unmask]
Date: Wednesday, November 13, 2013, 3:59 PM
Hi there,
Currently we use serum
(greiner tubes) for routine work however it appears that around 1 in 300 of our positive TnI results on repeating on the same specimen come back negative. We use a cut-off of 20ng/L and currently repeat all samples
above this to confirm the result. Negatives go straight out. The change noticed is beyond the 20ish% CV of the assay such that on some occasions results have been > 100ng/L but on repeat are <20ng/L. The samples are not spun prior to repeat testing. The cause
is proposed to be microclots which affect us due to our rapid analysis.
Do other users delay
analysis to allow for complete clotting or use plasma instead? Do any other labs repeat positive TnI on the same sample if serum or plasma is used to check for ‘flyers’?
Thank you for any
replies.
Steven
Steven
McCann FRCPath EurClinChem
Consultant
Clinical Biochemist and Clinical Biochemistry Lead Stepping Hill Hospital Poplar Grove Stockport NHS Foundation Trust
SK2
7JE
Tel No 0161
419 5619
Fax No 0161
419 5668
www.stockport.nhs.uk
www.nhslabmedservices.co.uk
------ACB discussion List Information-------- This is an open discussion list for the academic and clinical community working in clinical biochemistry.
Please note, archived messages are public and can be viewed via the internet. Views expressed are those of the individual and they are responsible for all message content.
ACB Web Site
http://www.acb.org.uk
Green Laboratories Work
http://www.laboratorymedicine.nhs.uk
List Archives
http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html
List Instructions (How to leave etc.)
http://www.jiscmail.ac.uk/
------ACB discussion List Information-------- This is an open discussion list for the academic and clinical community working in clinical biochemistry.
Please note, archived messages are public and can be viewed via the internet. Views expressed are those of the individual and they are responsible for all message content.
ACB Web Site
http://www.acb.org.uk
Green Laboratories Work
http://www.laboratorymedicine.nhs.uk
List Archives
http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html
List Instructions (How to leave etc.)
http://www.jiscmail.ac.uk/
This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom
they are addressed.
If you have received this email in error please notify the originator of the message. This footer also confirms that this
email message has been scanned for the presence of computer viruses but this should not be relied upon as a guarantee that the contents are virus free.
Any views expressed in this message are those of the individual sender, except where the sender specifies and with authority,
states them to be the views of the Norfolk and Norwich University Hospitals NHS Foundation Trust. The information contained in this e-mail may be subject to public disclosure
under the Freedom of Information Act 2000. Unless the information is legally exempt from disclosure, the confidentiality of this e-mail and your reply cannot be guaranteed
------ACB discussion List Information--------
This is an open discussion list for the academic and clinical community working in clinical biochemistry.
Please note, archived messages are public and can be viewed via the internet. Views expressed are those of the individual and they are responsible for all message content.
ACB Web Site
http://www.acb.org.uk
Green Laboratories Work
http://www.laboratorymedicine.nhs.uk
List Archives
http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html
List Instructions (How to leave etc.)
http://www.jiscmail.ac.uk/
|