Collection of biological samples in forensic toxicology

Abstract

Forensic toxicology is the study and practice of the application of toxicology to the purposes of the law. The relevance of any finding is determined, in the first instance, by the nature and integrity of the specimen(s) submitted for analysis. This means that there are several specific challenges to select and collect specimens for ante-mortem and post-mortem toxicology investigation. Post-mortem specimens may be numerous and can endow some special difficulties compared to clinical specimens, namely those resulting from autolytic and putrefactive changes. Storage stability is also an important issue to be considered during the pre-analytic phase, since its consideration should facilitate the assessment of sample quality and the analytical result obtained from that sample. The knowledge on degradation mechanisms and methods to increase storage stability may enable the forensic toxicologist to circumvent possible difficulties. Therefore, advantages and limitations of specimen preservation procedures are thoroughfully discussed in this review. Presently, harmonized protocols for sampling in suspected intoxications would have obvious utility. In the present article an overview is given on sampling procedures for routinely collected specimens as well as on alternative specimens that may provide additional information on the route and timing of exposure to a specific xenobiotic. Last, but not least, a discussion on possible bias that can influence the interpretation of toxicological results is provided. This comprehensive review article is intented as a significant help for forensic toxicologists to accomplish their frequently overwhelming mission.

Complete Republication: National Association of Medical Examiners Position Paper: Recommendations for the Investigation, Diagnosis, and Certification of Deaths Related to Opioid Drugs

“…External examination is an inadequate substitute for autopsy for the purposes of detecting and certifying drug caused deaths. The panel recommends that whenever a ME/C assumes jurisdiction in a death, the ME/C should also seek and assume jurisdiction over any laboratory specimens, such as blood, serum and urine, obtained prior to death by medical professionals [8].…”

“…Screening tests alone Application of heat to increase the rate of transfer of drug from transdermal patch to decedent Presence of naloxone offer only weak evidence, are subject to false negatives, and are inadequate for establishing a cause of death [11,12]. Therefore, the panel recommends performing toxicological analysis for controlled substances on all decedents for whom one or more of the following circumstances are true: Factors such as delay in autopsy, sampling technique, and specimen preservation contribute more to inaccuracies associated with toxicological testing than do the testing procedures themselves [16], but procuring and storing toxicology specimens under optimal conditions mitigate these factors [8,17]. The NAME standards call for collection of blood, urine, and vitreous humor as toxicology specimens in all cases whenever these specimens are available [5].…”

“…Because of postmortem redistribution of drugs, the best source of a blood sample for toxicological analysis is the iliofemoral vein [8,17]. Although some ME/Cs ligate the femoral vein and draw distal to the ligation under direct visualization, at least one study shows that samples drawn by blind stick access to the femoral vein yield closely comparable concentrations [18].…”

“…Although some ME/Cs ligate the femoral vein and draw distal to the ligation under direct visualization, at least one study shows that samples drawn by blind stick access to the femoral vein yield closely comparable concentrations [18]. If femoral vein blood is not available, then blood from the subclavian vein, the right atrium of the heart, or any other intact blood vessel is the next choice, listed in decreasing order of desirability [8]. Blood obtained from a body cavity is a specimen of last resort.…”

“…Sodium oxalate and sodium fluoride are the anticoagulant and preservative, respectively, of choice for blood for routine cases. Articles summarize and detail specimen selection, collection, and storage [8,17]. This list will change over time as pharmaceutical companies market new drugs or cease production of a drug that is currently available.…”