A Milan review found positive toxicology in 101 of 136 selected autopsies, or 74.3%. That did not mean 74.3% of all autopsied people used drugs, and it did not mean every positive result caused death. The series illustrates how referral for testing and causal assessment determine what an autopsy percentage means.
Only part of the autopsy population was tested
Di Candia and colleagues reviewed 2018–2019 cases at the University of Milan’s Bureau of Legal Medicine. There were 1,323 autopsies, but the Judicial Authority requested toxicological analysis in 136, approximately 10.3%.
The requests sought clarification of cause and manner of death. This selection process matters: a tested subgroup assembled for additional investigation is not a random sample of the general population, or necessarily of all autopsies. The other 1,187 cases were not 1,187 laboratory-negative observations.
What did a positive finding represent?
Samples were collected during autopsy and frozen at −20°C. Femoral and cardiac blood, urine and gastric contents were the principal matrices. Organs were examined in selected cases when conventional specimens were unavailable or further investigation was needed. The report does not provide a uniform death-to-collection interval for the series.
Testing used HPLC–MS/MS and GC–MS, with headspace testing for ethanol and volatile substances. The workflow distinguished initial library screening, further qualitative analysis and quantification using calibration standards. A reported positive was an analytical finding; assigning its role in death required another interpretive step.
Three denominators described three different results
Of the 136 tested cases, 101 were positive and 35 negative. The investigators classified 54 deaths as fatal acute intoxication using toxicology together with circumstances and autopsy findings.
Those 54 cases represented 39.7% of the tested series and 53.5% of the positive cases. They also represented approximately 4.1% of all 1,323 autopsies, although the paper rounds this overall proportion to 4.0%. These statements answer different questions and cannot be substituted for one another.
Positive findings in the remaining cases could still inform the investigation without constituting the primary poisoning diagnosis. Conversely, an untested autopsy cannot be counted as toxicologically negative simply to turn the overall proportion into an unbiased prevalence estimate.
A cross-country comparison needs comparable ascertainment
The authors discussed a lower overall intoxication proportion than in Finnish data, explicitly assuming that autopsies without requested toxicology could be treated as effectively negative. That assumption is a limitation, not a measured laboratory result.
Different testing policies, case referral, population coverage and definitions of drug-related death can alter apparent rates. This two-year, single-bureau retrospective review did not standardize those features across countries. It therefore cannot independently establish that one country’s population had a lower risk of fatal poisoning.
What the series supports
The findings demonstrate the usefulness of toxicology in selected medicolegal investigations. They do not establish a contemporary Milan-wide drug-use prevalence, a universal probability of poisoning after a positive test, or a drug concentration threshold for impairment.
When citing the percentages, preserve the testing decision, the matrix and the causal classification. In practical review, ask whether the numerator counts detections, positive cases or deaths attributed to intoxication, and whether the denominator is tested cases, positive cases or all autopsies. The distinction is also central to reconciling poisoning counts from death certificates and forensic files.
Primary source
Di Candia D, Giordano G, Boracchi M, Zoja R. Postmortem forensic toxicology cases: A retrospective review from Milan, Italy. Journal of Forensic Sciences. 2022;67:1640–1650. doi:10.1111/1556-4029.15050.
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