The impact of changing classifications on official fatal poisoning figures

Abstract

Background: Official mortality registers are of fundamental importance in research, however the comparability of data across countries and different versions of ICD (International Classification of Diseases) must be monitored. The aim of this article is to examine the impact of ICD coding rules, as there were three major updates between 2002 and 2010 affecting fatal poisoning data. Method: Data on all fatal poisonings registered by the Estonian Forensic Science Institute from 2000-2009 were coded according to ICD (effective in 2010), correspondence between forensic diagnosis and ICD categories and the impact of changes on ICD examined. Results: Priority lists to select the main substance in the case of multi-substance poisoning do not always result in the most dangerous drug. In particular, highly toxic fentanyles are rated below psychostimulants, which leads (in the case of Estonia) to significant distortion of drug-related mortality patterns. Implementation of the updates to ICD coding rules stating that aspiration may be due to other conditions results in a 16.8% increase in drug-related mortality. Tranquillizers such as benzodiazepines and barbiturates are absent from this list altogether. There are no guidelines to deal with surrogate alcohol. Conclusion: Implementation of the 2010 version of ICD must be carefully monitored by statistical authorities and researchers. The priority list for substances could be amended to give priority to fentanyles over psychostimulants and to frequently abused tranquillizers (benzodiazepines and barbiturates) over non-opioid analgesics. Certain combinations of toxic agents could have separate codes in ICD, especially if they have a coalitive effect.