Blood-positive illicit-drug findings: implications for cause-of-death certification, classification and coding

National cause-of-death data are important for national health administration, international comparisons and epidemiological research. The process of compiling mortality statistics starts with determination of causes of death, continues with medical death certification and concludes in coding of causes and selection of the underlying cause of death at statistical office. This study assesses how unequivocally and specifically the toxicologically verified intoxication of cannabinoids, opiates, amphetamines and cocaine is represented in diagnostic entries on death certificates and the national cause-of-death database and, ultimately, in the cause-of-death statistics. Drug-positive deaths, i.e. deaths with blood-positive drug finding(s), the corresponding death certificates and the information entered in Statistics Finland's cause-of-death database were reviewed for the entire years of 2000, 2002 and 2004. Drug influence at the time of death may or may not be related to death. A drug-related condition was reported as the cause of death in 52% of cannabinoid-positive, in 81% of amphetamine-positive, in 98% of opiate-positive and in 100% of cocaine-positive deaths, calculated from the combined three-year material. At Statistics Finland, after validation of the reported information, the distribution was practically the same. From the cause-of-death database, the specific drug-related diagnosis could be identified in 21% of cannabinoid-positive, in 89% of opiate-positive and in 57% of amphetamine-positive deaths. The corresponding proportions of specific drug-related underlying causes in the cause-of-death statistics were even smaller for cannabinoids and amphetamines, 10% and 39%, respectively. In multiple-drug cases, identification was possible only if each drug had been assigned an additional drug-specific code from "T categories" of ICD-10 Chapter XIX. What is noteworthy, however, is that a third of cannabinoid-related and a quarter amphetamine-related cause-of-death diagnoses were assigned unspecific categories of ICD-10 in the multiple-cause database and, more notably, in cause-of-death statistics based on selected underlying causes. For the better specification of drug-related causes of death, we propose that the next ICD revision provide each drug with the code of its own, e.g. one comparable to ATC (Anatomical Therapeutic Chemical Classification Index) codes, to be used for its specification in all positions and combinations, or at least provide compatibility with the ATC's coding system. For classification and describing the trends of drug-related deaths, equal and specific definitions for drug-related deaths would also be needed.