Association of Anatomical Pathology Technology


Variation in sampling – The death of post-mortem toxicology?

Variation in sampling – The death of post-mortem toxicology?

Jennifer Button
Pharma, Phytochemistry, Forensic and Clinical Sector, LGC Standards, Middlesex, UK

Stephen Morley
Toxicology Section, Clinical Chemistry Department, Royal Hallamshire Hospital, Sheffield, UK

Atholl Johnston
Analytical Services Limited, St George’s – University of London, London, UK

Ishbel Gall
Association of Anatomical Pathology Technology, Coldbath Square, London, UK

Michelle Lancaster
Association of Anatomical Pathology Technology, Coldbath Square, London, UK

Introduction: For post-mortem toxicology, lack of harmonisation between practices such as preferred sample, location and method of sampling can have significant impact on the interpretation of results. For toxicology, as with computing, ‘garbage in, garbage out’, is true as an analytical result - or its interpretation - can never be better than the sample from which it is derived. A recent pilot study explored variation in post-mortem liver sampling and its implications for post-mortem toxicology interpretation1, but we describe here the first comprehensive survey examining post-mortem sampling strategies for toxicological analysis. The main purpose of this survey was to ascertain the current level of understanding and practice of Anatomical Pathology Technologists (APTs) with regards post-mortem toxicology sampling in the UK and Irish Republic.

Methods: In Autumn 2012 a questionnaire was circulated, via SurveyMonkey, to members of the Association of Anatomical Pathology Technology (AAPT), a professional body for APTs employed in hospital and public mortuaries. Participants were instructed respond to questions from the best of their knowledge; providing typical examples of practice in their own mortuary and where necessary involving a pathologist to assist.

Results: Responses were obtained from 63 AAPT members (response rate 25%). It is likely that a proportion of these responses represent a mortuary rather than an individual. The highest response rate was from the South of England (43%). From those surveyed it appears that APTs, not pathologists, are primarily responsible for sampling during routine (non-forensic) post-mortems (94%). The samples most frequently collected are blood, urine and vitreous humour (100, 95 and 62%). Blood was routinely sampled from the heart by 3% of respondents. Ligation of the femoral vein was routinely carried out by only 13% of APTs. Stomach content was sampled more frequently than liver (41% versus 29%). There was a good understanding in the prioritisation hierarchy of blood sampling site for quantitative toxicology, but in the majority the sampling site for liver was not optimal. A quarter of respondents (25%) did not specify the site of sampling on the container or submission form. Where sample volume was limited there was divided opinion on whether to preserve (56%) or not to preserve (44%). The preservative of choice was fluoride oxalate (82%). Over half of the population surveyed (54%) were unaware of any standards for best practice on post-mortem sampling in toxicology and 50% would like more guidance. This was primarily believed to be the responsibility of the toxicology service provider.

Discussion: The increased emphasis on laboratory accreditation and measurement uncertainty is, to a large degree fruitless unless attempts are made to address pre-analytic error, such as incorrect, inconsistent or undocumented sampling practices. The effects of non-routine sampling and post-mortem redistribution are well understood among the toxicology community; however it is the authors’ perception that currently there is greater focus on ensuring appropriate caveats are applied to reporting than minimising the occurrence. Whilst we acknowledge that these issues cannot be eliminated entirely, appropriate steps should be taken to reduce their contribution to uncertainty.

Conclusion: Better communication and reciprocal training is required between the post-mortem room and toxicology laboratories on post-mortem sampling strategies. Beyond traditional customer-service provider arrangements, professional bodies for toxicology and pathology should collaborate to this effect. Joint, universal guidelines and raised awareness of their existence would be one such way forward. 

Key Words: Post-mortem, Sampling, Redistribution

1Steven R Morley & Jennifer Bolton. Variation in post-mortem liver sampling: implications for postmortem toxicology interpretation. J Clin Pathol. 2012 Dec;65(12):1136-7. doi: 10.1136/jclinpath-2012-200980. Epub 2012 Aug 10.

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