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1. Ammonia in plasma exists in equilibrium with the ammonium anion. Ammonia is also present in the atmosphere. When the sample is collected there is the possibility of the equilibrium being disturbed by the addition or loss of ammonia to the air space. To mitigate against this affect we only analyse samples that arrive in the lab within 15 minutes of collection. You could reject grossly under-filled specimens but my experience is that such specimens are likely to be haemolysed and so would be rejected on that basis - ammonia is present in red cells at ~3 times the concentration of plasma. 2. The key step is to separate the plasma from the cells. Once that has happened ammonia still increases due to deamination reactions but at a slower rate. Low temperatures retard these reactions and so increase the stability. We allow promptly separated plasma to be refrigerated if it can be analysed within 2 hours, otherwise it should be frozen. Gavin On 28 April 2016 at 14:00, Pullan Nicola (ROYAL UNITED HOSPITALS BATH NHS FOUNDATION TRUST) <[log in to unmask]> wrote: > Hello, > > Can anyone help with the following? > > 1. Our pack insert (Cobas) states that EDTA blood tubes should be > full for ammonia analysis. We make no provision for this currently and > don't bounce requests if the bottles are under-filled. Any opinion? > > 2. If samples are separated from the cells and aliquoted into a > sealed false bottomed tube for analysis at a later point e.g. if analyser > out of action, any idea of stability? > > Many thanks for any answers in advance. > > Best wishes, > > Nicola > Nicola Pullan > Principal Clinical Biochemist > Royal United Hospitals Bath NHS Foundation Trust > Combe Park, Bath, BA1 3NG > Dir Line: 01225 824711 > Visit our website at: www.ruh.nhs.uk/pathology > > > > > ******************************************************************************************************************** > > This message may contain confidential information. If you are not the > intended recipient please inform the > sender that you have received the message in error before deleting it. > Please do not disclose, copy or distribute information in this e-mail or > take any action in reliance on its contents: > to do so is strictly prohibited and may be unlawful. > > Thank you for your co-operation. > > NHSmail is the secure email and directory service available for all NHS > staff in England and Scotland > NHSmail is approved for exchanging patient data and other sensitive > information with NHSmail and GSi recipients > NHSmail provides an email address for your career in the NHS and can be > accessed anywhere > > > ******************************************************************************************************************** > > ------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/