Postmortem metabolomics: influence of time since death on the level of endogenous compounds in human femoral blood. Necessary to be considered in metabolome study planning?

INTRODUCTION: The (un)targeted analysis of endogenous compounds has gained interest in the field of forensic postmortem investigations. The blood metabolome is influenced by many factors, and postmortem specimens are considered particularly challenging due to unpredictable decomposition processes. OBJECTIVES: This study aimed to systematically investigate the influence of the time since death on endogenous compounds and its relevance in designing postmortem metabolome studies. METHODS: Femoral blood samples of 427 authentic postmortem cases, were collected at two time points after death (854 samples in total; t1: admission to the institute, 1.3-290 h; t2: autopsy, 11-478 h; median ∆t = 71 h). All samples were analyzed using an untargeted metabolome approach, and peak areas were determined for 38 compounds (acylcarnitines, amino acids, phospholipids, and others). Differences between t2 and t1 were assessed by Wilcoxon signed-ranked test (p < 0.05). Moreover, all samples (n = 854) were binned into time groups (6 h, 12 h, or 24 h intervals) and compared by Kruskal-Wallis/Dunn's multiple comparison tests (p < 0.05 each) to investigate the effect of the estimated time since death. RESULTS: Except for serine, threonine, and PC 34:1, all tested analytes revealed statistically significant changes between t1 and t2 (highest median increase 166%). Unpaired analysis of all 854 blood samples in-between groups indicated similar results. Significant differences were typically observed between blood samples collected within the first and later than 48 h after death, respectively. CONCLUSIONS: To improve the consistency of comprehensive data evaluation in postmortem metabolome studies, it seems advisable to only include specimens collected within the first 2 days after death.

A retrospective review of methylamphetamine detected in child deaths reported to the Victorian Coroner, Australia.

This study investigated methylamphetamine (MA) exposures in the deaths of children (≤ 12 years old) reported to the Coroner in the state of Victoria, Australia, between 2011 and 2020. Demographics, autopsy findings including the cause of death, self-reported prenatal or caregiver drug use, child protection services information, and toxicological findings were summarized by descriptive statistics. Validated methods of liquid chromatography-tandem mass spectrometry were used in the analysis of drugs. There were 50 child deaths with MA detected in blood, urine, and/or hair with 64% (n = 32) identified in 2018-2020. Most children were 1-365 days old (66%, n = 33) and the cause of death was unascertained in 62% (n = 31) of cases. MA was toxicologically confirmed in hair (94%, n = 47) significantly more than blood (18%, n = 9). Prenatal or caregiver drug use was self-reported in 44% (n = 22) and 42% (n = 21) of cases, respectively. Moreover, only 54% (n = 27) of deceased children were a child protection client at their time of death. These findings suggest the number of deceased children exposed to MA has increased over the past 10 years, which is consistent with the greater supply of crystal MA in the Australian community. Hair analysis provided additional means to identify cases that were unknown to child protection services and may have implications for other children in the same drug exposure environment.

Quantitative analysis of tetrahydrocannabinol isomers and other toxicologically relevant drugs in blood.

A multi-analyte liquid chromatography-tandem mass spectrometry (LC-MS/MS) method is described, involving the separation of delta-9-tetrahydrocannabinol (delta-9-THC) and delta-8-THC in addition to other commonly encountered drugs and metabolites. Briefly, sample preparation involved an alkaline liquid-liquid extraction (methyl tert-butyl ether) of blood (100 µl). The solvent layer was transferred, evaporated to dryness, reconstituted, and samples then separated on an Agilent Poroshell 120 EC-C18 100 Å (50 mm × 3.0 mm, 2.7 µm) analytical column using a multi-step gradient elution of 50 mM ammonium formate in water (pH 3.5) and 0.1% formic acid in methanol over 14 min. A SCIEX Triple Quad 6500+ system operating in scheduled multiple reaction monitoring and positive electrospray ionization was used for detection. There were no interferences, and matrix effects were generally acceptable (±20% of neat response). Linearity was achieved within the calibration range, including methylamphetamine (MA) (10-1000 ng/ml), 3,4-methylenedioxy-N-methylamphetamine (MDMA) (10-1,000 ng/ml), cocaine (10-1000 ng/ml), and two THC isomers (1-100 ng/ml). Accuracies of MA, MDMA, cocaine, and two THC isomers were 3.6 to 8.9%, -1.2 to 4%, -5.3 to 5.8%, and -11 to 14%, respectively; while precision estimates of the same were 1.6 to 5.4%, 1.7 to 5.3%, 1.2 to 4.5%, and 2 to 10%, respectively. Autosampler stability and dilution integrity were within acceptable limits, and no carryover was detected at the limit of detection. This validated LC-MS/MS method made the routine identification of both delta-9-THC and delta-8-THC in blood possible.

Methylamphetamine toxicity and its involvement in death: A retrospective observational study of deaths reported to the Victorian Coroner, Australia.

A retrospective observational study of Victorian deaths involving MA between 2010 and 2019 was conducted to determine the prevalence and contribution of methylamphetamine (MA) toxicity to death in the absence of other factors. Demographics, autopsy findings, toxicology, and the cause of death were reviewed. Coronial cases were categorized into five groups: deaths due to MA toxicity in the absence of other factors (Group A1); deaths due to MA toxicity in the setting of other potentially contributing factors (Group A2); deaths due to MA toxicity in the setting of significant natural disease (Group B); deaths primarily due to multiple-drug toxicity (Group C); and deaths primarily due to natural causes (Group D). There were 506 deaths involving MA categorized into Group A1 (n = 1, 0.6%), Group A2 (n = 8, 1.6%), Group B (n = 28, 5.5%), Group C (n = 229, 45%), and Group D (n = 240, 47%). Significant natural disease was prevalent among deaths involving MA and mainly concerned forms of cardiovascular disease (n = 277, 55%). The MA concentration in the one death included in Group A1 was 2.1 mg/L. The median MA concentrations of Group A2 (1.6 mg/L) and Group B (0.5 mg/L) were significantly higher than Group C (0.2 mg/L) and Group D (0.2 mg/L). Additionally, many other toxicologically significant drugs were detected and mostly comprised of central nervous system depressants. Deaths due to MA toxicity in the absence of other factors were rare despite the greater availability of crystal MA in the Australian community. The study highlights the interpretative challenges of MA blood concentrations and the continuing harms of this drug in Australia.

Stimulant use in suicides: A systematic review.

Suicide remains a global public health concern and the increased supply and use of synthetic stimulants globally may have implications for the burden of suicides attributable to substance use. This systematic review investigated any potential associations of stimulant use detected in post-mortem biological specimens and suicides. We conducted a systematic review and narrative synthesis (CRD42021237966). Medline, EMBASE, TOXLINE, and Scopus databases were searched for terms related to forensic toxicology, post-mortem toxicology, suicide and stimulants. The primary outcome was to estimate the prevalence of stimulant use in suicides. There were 26 studies whichcontributed to prevalence measures; in studies reporting at the individual compound level, suicides involved cocaine (0.1-23%), caffeine (3.2-22%), 3,4-methylenedioxymethamphetamine (0.1-17%), amphetamine (0.2-9.3%), methamphetamine (3.1-7%), and phentermine (0.9-1%). Overall, stimulant use in suicides was over-represented compared to estimates of stimulant use in the general population and has increased over time. Thirteen case reports used to contextualise suicides involving stimulants found no examples of cocaine or methamphetamine mono-intoxication of suicidal intent. This suggests mechanisms other than acute toxicity involved in stimulant-associated suicide. Future research by in-depth psychological autopsies of suicides involving stimulants, in combination with segmental hair analysis to determine the chronicity of stimulant exposure, may contribute to a better understanding of the burden of suicide attributable to stimulant use.

Postmortem Metabolomics: Strategies to Assess Time-Dependent Postmortem Changes of Diazepam, Nordiazepam, Morphine, Codeine, Mirtazapine and Citalopram.

Postmortem redistribution (PMR) can result in artificial drug concentration changes following death and complicate forensic case interpretation. Currently, no accurate methods for PMR prediction exist. Hence, alternative strategies were developed investigating the time-dependent postmortem behavior of diazepam, nordiazepam, morphine, codeine, mirtazapine and citalopram. For 477 authentic postmortem cases, femoral blood samples were collected at two postmortem time-points. All samples were quantified for drugs of abuse (targeted; liquid chromatography-tandem mass spectrometry LC-MS/MS) and characterized for small endogenous molecules (untargeted; gas chromatography-high resolution MS (GC-HRMS). Trends for significant time-dependent concentration decreases (diazepam (n = 137), nordiazepam (n = 126)), increases (mirtazapine (n = 55), citalopram (n = 50)) or minimal median postmortem changes (morphine (n = 122), codeine (n = 92)) could be observed. Robust mathematical mixed effect models were created for the generalized postmortem behavior of diazepam and nordiazepam, which could be used to back-calculate drug concentrations towards a time-point closer to the estimated time of death (caution: inter-individual variability). Significant correlations between time-dependent concentration changes of morphine, mirtazapine and citalopram with individual endogenous molecules could be determined; no correlation was deemed strong enough for successful a posteriori estimation on the occurrence of PMR for specific cases. The current dataset did successfully lead to a significant knowledge gain in further understanding the time-dependent postmortem behavior of the studied drugs (of abuse).

High Throughput Detection of 327 Drugs in Blood by LC-MS-MS with Automated Data Processing.

The described procedure provides a rapid technique for the detection and semi-quantitation of a large number of drugs in blood. This procedure uses a minimal sample volume and employs a one-step liquid extraction and automated data processing to yield rapid turnaround times. A total of 327 of the most commonly used medicinal and illicit drugs in Australia were selected including various amphetamines, anesthetics, antidepressants, antipsychotics, anticonvulsants, benzodiazepines, beta blockers, opioid and nonopioid analgesics, stimulants, THC and a large number of synthetic cannabinoids and other novel psychoactive substances. The extracts were subject to 5-minute chromatography using a Kinetex C18 50 × 4.6 mm 2.6 µm solid-core analytical column and analyzed using a Sciex 3200 Q-TRAP MS-MS (+ ESI, MRM mode, two transitions per analyte). The method was fully validated in accordance with international guidelines. Matrix effects and extraction efficiencies were acceptable with most analytes showing > 80% response and low variation (within 25%RSD). Cannabinoids were most affected by the matrix and yielded poorest recovery values but were still detectable. Precision, accuracy, repeatability and multipoint linearity were assessed for all analytes. The method has been used in routine practice in the forensic toxicology service at the Victorian Institute of Forensic Medicine in over 6000 coronial investigations using both postmortem and clinical blood specimens. This technique has greatly increased throughput, reduced turnaround times and allowed for rapid same-day analysis of results when needed. The method is routinely used in routine overnight testing with results reported to pathologists within 4 h of data acquisition. This rapid toxicological technique is used in conjunction with other investigative processes such as full-body CT imaging, review of case circumstances and medical histories to provide an efficient death investigation process.

Time-Dependent Changes in THC Concentrations in Deceased Persons.

Changes in the concentrations of Δ9-tetrahydrocannabinol (THC) in the postmortem period were investigated in a series of cases by comparing concentrations in blood taken on receipt of the body in the mortuary (admission specimen, AD) with the concentrations obtained in blood taken at autopsy some time later and also from blood specimens taken antemortem. Overall, the median THC concentration in AD blood was 13.7 ng/mL (n = 239, range LOQ-220), while the median concentration at autopsy was 13.8 ng/mL (n = 106, range LOQ-810) and 1.9 ng/mL (n = 147, range LOQ-48) antemortem. Fourteen cases had all three specimens taken from the same decedent. The corresponding AM, AD and PM median concentrations were 4.0 (range LOQ-48), 15.5 (range 4.0-176) and 4.4 ng/mL (LOQ-56), respectively. The median elapsed times from AM to AD and AD to PM were 33 and 97.5 h, respectively. In contrast, acetaminophen showed no change in blood concentration from AM to AD (6.8 and 6.0 mg/L, respectively). These data show large increases in THC concentration in the early postmortem period, followed by a decline, although the median blood concentrations at autopsy were similar to that obtained antemortem. In contrast, when blood was taken from the femoral region, subclavian and heart ventricles sites, in the same case, the THC concentrations, while variable, showed overall no significant difference. These dynamic changes reflect complex phenomenon occurring in deceased persons and will further serve to increase the uncertainty over any interpretation of postmortem THC concentrations.

Postmortem Drug Redistribution: A Compilation of Postmortem/Antemortem Drug Concentration Ratios.

Postmortem drug redistribution (PMR) is a well-known phenomenon in forensic toxicology with implications for medico-legal death investigations. Paired antemortem (AM) specimen and postmortem (PM) mortuary admission femoral blood drug concentrations from 811 coronial cases were used to construct a retrospective compilation of PM/AM drug concentration ratios for 42 parent drugs and metabolites. The median PM/AM ratios for all antidepressants were > 1 and consistent with PMR In contrast, the median PM/AM ratios of most benzodiazepines were < 1. The antipsychotics were varied (0.63-3.3) and suggest the mixed effects of PMR and drug instability. Amphetamines exhibited no trends (0.90-0.95) and are likely confounded by many factors. The PM/AM ratios of cardiovascular drugs, opioids and other drugs are also reported. This research represents an expansive retrospective compilation of paired AM and PM drug concentrations for many toxicologically relevant drugs. While the median PM/AM ratios demonstrate some drug-dependent trends, there was no obvious relationship between AM specimens and PM femoral blood taken at mortuary admission.

A systematic investigation of forensic hair decontamination procedures and their limitations.

The effectiveness of decontamination procedures used for the removal of external drug contamination in forensic hair analysis is an ongoing debate. This investigation evaluated wash methods complying with Society of Hair Testing (SoHT) guidelines and their capacity to remove cocaine (COC) and methamphetamine (MA) from artificially contaminated hair. The most effective decontamination method was determined using a systematic approach, involving (1) an initial washing solvent screen, (2) optimization of wash duration, (3) comparison of sequential wash methods, and (4) reanalysis of clinical hair samples. For analysis, hair was subjected to micro-pulverized methanolic extraction prior to quantitation by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Methanol (MeOH) and 0.1 M phosphate buffer (pH 6) were the most effective organic and aqueous solvents, respectively, removing 28%-38% of COC and 16%-31% of MA. Wash durations longer than 30-60 minutes did not remove additional amounts, and a more efficient sequential wash method was subsequently developed. Despite this, the interpretation of reportable results relative to the SoHT cut-off levels was unchanged for most clinical hair samples reanalyzed after washing by agitation for 30 minutes with MeOH. These findings highlight the inability of decontamination solvents to completely remove external COC and MA contamination from hair, including wash methods adhering to SoHT guidelines.

The effectiveness of decontamination procedures used in forensic hair analysis.

Hair is a mainstream specimen used in forensic toxicology to determine drug use and exposure. However, the interpretation of an analytical hair result can be complicated by the presence of external drug contamination. Decontamination procedures are included in hair analysis methods to remove external contamination, but the capacity of these washes to completely remove contamination for all drugs is controversial. It is evident that there is no consensus on the most effective decontamination procedure, nor can decontamination procedures consistently remove external drug contamination to less than reportable cut-offs for all analytes. ∆9-tetrahydrocannabinol deposited from cannabis smoke is mostly removed by organic solvents, whereas ionizable drugs are more effectively removed by an aqueous wash. Organizations such as the Society of Hair Testing recommend a hair decontamination procedure should include both an organic and aqueous washing step, which is in accordance with the reviewed literature. Studies involving a systematic evaluation of various solvents have shown that the most effective organic solvent was methanol and the most effective aqueous solvent contained sodium dodecyl sulfate detergent. If future systematic studies can demonstrate similar findings, a consensus on the most effective decontamination procedure for forensic hair analysis may be established.