A drug listed in a postmortem surveillance study may be a confirmed finding or an explicitly unconfirmed screening result. Those categories should remain distinct. In a 4,395-case Ontario fentanyl series, some newly encountered substances were reported after a single analytical run, and the authors included those findings with that qualification.
What population the counts describe
The retrospective study covered investigations submitted to the Centre of Forensic Sciences between January 2020 and December 2022. Inclusion required fentanyl quantified above 1.3 ng/mL in autopsy blood from an intact vessel or an antemortem hospital sample. Most specimens were femoral blood, but approximately 11% were heart blood, hospital samples or an unspecified source.
The series was selected for measurable fentanyl. It cannot estimate the prevalence of another drug among all deaths, all drug users or the general population. There was also no living comparison group from which to calculate the added fatal risk of a particular combination.
The study’s confirmation rule
Drug screening used liquid chromatography–quadrupole time-of-flight mass spectrometry, or LC–QTOF-MS. Under the laboratory’s reporting criteria, a detected drug was supported either by two independent LC–QTOF-MS analyses or by one LC–QTOF-MS analysis plus an orthogonal method, such as GC–MS or LC–MS/MS.
A small proportion of findings, described as less than 5%, were supplied to clients after a single LC–QTOF-MS analysis and labeled unconfirmed. A client could request follow-up testing. The article explained that the service selected and the needs of the death investigation influenced how extensively all detected compounds were pursued.
Thus, “confirmed” did not necessarily mean two different instrument technologies: two independent LC–QTOF-MS analyses also met the stated rule. Conversely, a plausible single-run signal did not become confirmed merely because other drugs in that case were confirmed.
The counts need their analytical labels
The study reported frequent co-occurrence of novel benzodiazepines, including etizolam in 642 cases, flualprazolam in 531 and bromazolam in 138. Synthetic opioid findings included isotonitazene in 30 cases and metonitazene in 27. Confirmation patterns varied across compounds and time.
Six protonitazene findings were reported only as unconfirmed results. They should not be restated as six fully confirmed protonitazene deaths. Nor does the absence of completed confirmation prove that those detections were false. It limits the strength of the identification claim available from this dataset.
In the selected case with estimated fentanyl above 2,000 ng/mL, acetylfentanyl, bromazolam, cocaethylene and metonitazene were identified by LC–QTOF-MS but not confirmed by a second independent analysis. The authors preserved that qualification while reporting mixed drug intoxication as the cause of death.
Testing practices affect apparent trends
A rising count can reflect changes in exposure, analytical scope, identification capability, follow-up testing or some combination of these. The paper specifically identified the proliferation of new substances and reporting practices as interpretive challenges. It did not establish a numerical correction that separates those influences.
The fentanyl quantitation method had its own detection limits, which changed during the study, while the LC–QTOF-MS screen used predefined identification criteria rather than a single stated detection limit. The quantitative fentanyl inclusion rule cannot be treated as the sensitivity threshold for every co-occurring substance.
The available histories also did not establish the source of fentanyl in every case. Co-detection alone does not show that substances came from one product, were deliberately combined or were consumed at the same moment.
What a defensible summary says
A useful summary identifies the selected cohort, specimen mix, reporting category and confirmation status. It distinguishes a laboratory signal from a quantified concentration, and both from the pathologist’s assessment of contribution to death.
For related testing-scope questions, see why an opiate screen may not test for fentanyl and what a negative autopsy screen can exclude. Neither positive nor negative results answer more than the method and case evidence support.
Primary source
Adamo A, Marshall K, Woodall KL. Fentanyl-related deaths in Ontario, Canada: toxicological findings and circumstances of death in 4395 cases (2020–22). Journal of Analytical Toxicology. 2024;48:598–605. https://doi.org/10.1093/jat/bkae061.
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