Fatal drug poisonings: medico-legal reports and mortality statistics
Introduction
In Finland, all deaths suspected to be due to poisoning are submitted to medico-legal cause-of-death determination [1]. This practice systematically includes forensic toxicological examination. These post-mortem examinations are centralized [2] to an authorized toxicological laboratory at the Forensic Toxicology Division (FTD) of the Department of Forensic Medicine, University of Helsinki, which guarantees virtually complete national coverage of fatal poisonings and as such the quality and homogeneity of results for subsequent use in epidemiological and other kinds of drug-specific studies.
Medical examiners provide the FTD with a copy of their final report, i.e. the death certificate, of each death for which a toxicological examination is performed. In addition to their own laboratory results, the FTD register contains a medico-legal statement on the cause(s)- and manner-of-death, i.e. whether the death was considered to be an accident, suicide, homicide, undetermined or natural by the medical examiner.
Finnish official mortality statistics, based on the same death certificates, are collected at Statistics Finland (SF), after possible consultation of an expert panel [3] and/or querying the certifier for additional information [4], in accordance with World Health Organization (WHO) principles and notes [5], [6], and internal guidelines. WHO defines the causes of death to be entered on the death certificate as “all those diseases, morbid conditions or injuries which either resulted in or contributed to death and the circumstances of the accident or violence which produced any such injuries”. The cause for primary tabulation, designated the underlying cause-of-death, is defined as “(a) the disease or injury which initiated the train of events leading directly to death, or (b) the circumstances of the accident or violence which produced the final injury” [5]. At SF, the 10th revision of the Statistical International Classification of Diseases (ICD-10) and Related Health Problems [6] is used to code the certified causes of death and to select the underlying cause-of-death. ICD-10 is divided into 21 sections, designated with Roman numerals. Sections I–XVII cover diseases and other morbid conditions, and section XVIII symptoms and signs. Section XIX categorizes injuries, poisonings and other consequences of external causes. Section XX, external causes of mortality (and morbidity), is primarily used to classify causes of injury and poisoning. The sections are subdivided into blocks, and each block into categories, with code numbers of their own. To describe a fatal injury, poisoning or other consequence of external cause for mortality statistics, two codes are applicable: a code from section XIX describing the nature of the injury, and a code from section XX describing the external cause, e.g. a suicide by overdose of insulin is coded at three-character level with X64 (for suicide) and T38 (for insulin poisoning). In mortality tabulation of underlying cause-of-death, the manner-of-death, i.e. code X64 in the example above, is the primary code.
When death certification is correct, it is likely that the selected underlying cause-of-death agrees, before possible modification according to WHO regulations, with the originating antecedent cause-of-death as stated by the medical examiner. From a medico-legal as well as a statistical point of view, the correct determination of the cause and manner of a suspected fatal drug poisoning is essential. In general, the presence and quantity of poisonous common drugs in deceased persons can routinely be verified by modern toxicological methods. But, even when a suspicion of drug overdose arises from laboratory findings, drug poisoning as the cause-of-death cannot only be a “laboratory diagnosis”; anamnestic information, circumstances surrounding the death, autopsy findings and toxicological results together are necessary for a forensic examiner to form a justified, evidence-based opinion about the manner and cause(s) of death. The problems, if any, usually arise with multiple-drug poisonings. The medical examiner must identify the principal component from among a combination of toxicants when certifying the death, and the statistics office must correctly, according to the ICD regulations, select and code the underlying cause-of-death.
As far as we know, a comparison of fatal drug poisonings by drug-specific toxicological diagnoses on death certificates with registered cause-of-death poisonings has not been published earlier. At the rougher main category level of ICD-10, in the Finnish cause-of-death data from 1995, the disagreement rate between certified and registered causes of death overall was 29.4%, and the false-positive and false-negative rates for all fatal poisonings were 13.8 and 35.9%, respectively [3]. In multiple-toxicant poisonings, the effect on the number of fatal drug poisonings of the ICD-10 regulation of coding “to the medicinal agent when combined with alcohol” has not yet been clarified.
Section snippets
Materials and methods
The study material consists of all deaths from drug poisoning in 1997, as reported by the medical examiner after toxicological analyses at the FTD, for a total of 504 deaths. Of these, 18 deaths were excluded because the death had occurred in 1996 and 14 deaths from the 1998 register were added since they were pronounced in 1997. The final number of deaths in the FTD material is 500.
Each of these 500 medico-legally proven fatal poisonings were matched with the corresponding cause-of-death
Accidents
Accidental deaths numbered 99, comprising 19.8% of all fatal drug poisonings; 62 (62.6%) were male and 37 (37.4%) female deaths. The mean age was 46 years, for males 39.4 (range 18–65) years and for females 57.1 (range 29–92) years.
At the manner-of-death level, the SF agreed with 79 (79.8%) of these 99 deaths, coding them as accidents (Table 2). Three deaths (3.0%) were re-assigned to corresponding suicide categories, but 17 deaths (17.2%) were regarded as being of natural origin, mostly due to
Discussion
The pathway from findings to compiling mortality statistics is a long winding one, from medical cause-of-death determination via death certification, selection and coding of causes of death, to the cause-of-death register and mortality statistics.
With regard to suspected poisoning deaths, like all other unnatural deaths, the medical portion of this chain of events in Finland is attended by medical examiners within a nation-wide specialized, adequately occupied and facilitated provincial or
Acknowledgements
Our gratitude is due to Riitta Harala, Director of Population Statistics, and Hilkka Ahonen, Senior Statistician, of Statistics Finland, for the cause-of-death data from 1997 (permit TK-53-1783-99). Helena Liuha, Kaija Saarela and Tarja Ruotsalainen of the Department of Forensic Medicine, University of Helsinki, are thanked for their unselfish practical assistance. We also thank Carol Ann Pelli for linguistic revision.
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