Using textual cause-of-death data to study drug poisoning deaths

Death certificate data are often used to study the epidemiology of poisoning deaths, but the International Classification of Diseases (ICD) codes used to tabulate death data do not convey all of the available information about the drugs and other substances named on death certificates. In the United States and some other countries, the SuperMICAR computer system is used to assign ICD codes to deaths. The SuperMICAR system also stores a verbatim record of the text entered for the cause of death. We used the SuperMICAR text entries to study the 7,817 poisoning deaths that occurred among Washington State residents between 2003 and 2010. We tabulated the drugs named on death certificates and computed age-adjusted and age-specific death rates for the top-named drugs and for prescription and illicit drugs. Methadone was named on 2,149 death certificates and was the most frequently named substance, followed by alcohol, opiate, cocaine, oxycodone, and methamphetamine. For both men and women and at all ages, prescription drugs were involved in more deaths than were illicit drugs. Among the 25 drugs named most frequently, only 4 have unique ICD codes; the other 21 can be identified only by using the SuperMICAR data.