Classifying undetermined poisoning deaths.

OBJECTIVE: To classify poisoning deaths of undetermined intent as either suicide or unintentional and to estimate the extent of underreported poisoning suicides.
METHODS: Based on 2002 statewide death certificate and medical examiner data in Utah, the authors randomly selected one half of undetermined and unintentional poisoning deaths for data abstraction and included all suicides. Bivariate analyses assessed differences in demographics, death characteristics, forensic toxicology results, mental health history, and other potentially contributing factors. Classification and regression tree (CART) analysis used information from unintentional and suicide poisoning deaths to create a classification tree that was applied to undetermined poisoning deaths.
RESULTS: The authors analyzed 41 unintentional, 87 suicide, and 84 undetermined poisonings. Undetermined and unintentional decedents were similar in the presence of opiates, physical health problems, and drug abuse. Although none of the undetermined decedents left a suicide note, previous attempt or intent to commit suicide was reported for 11 (13%) of these cases. CART analysis identified suicidal behavior, drug abuse, physical health problems, depressed mood, and age as discriminating between suicide and unintentional poisoning. It is estimated that suicide rates related to poisoning are underreported by approximately 30% and overall suicide rates by 10%. Unintentional poisoning death rates were underreported by 61%.
CONCLUSIONS: This study suggests that manner of death determination relies on circumstance dependent variables that may not be consistently captured by medical examiners. Underreporting of suicide rates has important implications in policy development, research funding, and evaluation of prevention programs.