A multidimensional assessment of the validity and utility of alcohol use disorder severity as determined by item response theory modelsDrug and Alcohol Dependence Article in Press, 29 September 2009
The relative severity of the 11 DSM-IV alcohol use disorder (AUD) criteria are represented by their severity threshold scores, an item response theory (IRT) model parameter inversely proportional to their prevalence. These scores can be used to create a continuous severity measure comprising the total number of criteria endorsed, each weighted by its relative severity
The unadjusted mean values for all validating measures increased steadily with the severity threshold score, except that legal problems, the criterion with the highest score, was associated with lower values than expected. After adjusting for the total number of criteria endorsed, this direct relationship was no longer evident. The overall severity score was no more highly correlated with the validating measures than a simple count of criteria endorsed, nor did the two measures yield different risk curves. This reflects both within-criterion variation in severity and the fact that the number of criteria endorsed and their severity are so highly correlated that severity is essentially redundant.
Attempts to formulate a scalar measure of AUD will do as well by relying on simple counts of criteria or symptom items as by using scales weighted by IRT measures of severity.
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