The concepts of the new criteria for Yusho poisoning

Background: The current diagnostic criteria for Yusho poisoning do not include dioxin levels, although one of the subgroups of dioxins, polychlorinated dibenzofurans, was shown to contribute the most to the total toxic equivalent quantity in the blood of Yusho patients. Objective: To propose new diagnostic criteria for Yusho using blood dioxin levels. Subjects and methods: Participants of the nationwide health examination for Yusho in 2001 and 2002, and randomly selected residents of Fukuoka City, Japan, were included in this study. A multiplicative model was applied to blood 2,3,4,7,8-pentachlorodibenzofuran (PeCDF) level with age and sex as explanatory variables. A logistic regression model including 2,3,4,7,8-PeCDF level, age and sex was also used. Results: Three criteria are proposed based on different approaches: 2,3,4,7,8-PeCDF level adjusted for age and sex (criterion 1), its one-tailed upper prediction limit (criterion 2), and the estimated probability of being a Yusho patient (criterion 3). By applying these three criteria to potential victims who had not been diagnosed as having Yusho according to the current diagnostic criteria, the same people were identified as Yusho sufferers. Criterion 1 with an upper 99 percentile of age- and sex-adjusted 2,3,4,7,8-PeCDF level of controls as a cut-off was determined, from a practical perspective, to be superior to the other criteria.