Recent research by Kahler et al. (2003) and Krueger et al. (2004) using Item Response Theory (IRT; Lord, 1980) has provided an important alternative method to represent alcohol severity. IRT offers a number of improvements upon the additive approach embodied in scales such as the ADS or DSM-IV syndromes, particularly in that these methods allow a better delineation of the properties of various markers of a latent trait at different levels of that trait. Kahler et al. found that whereas some ADS items appeared to have limited ability to make reliable discriminations at different levels of alcohol dependence, a subset of 12 items provided solid coverage across this continuum. These authors noted that the establishment of these level estimates not only informs the refinement of the scale, but also may offer information about the potential developmental progression of symptoms in the alcohol dependence syndrome. They noted that Langenbucher and Chung’s (1995) survival analyses of age of onset of the DSM criteria implied a similar progression. Krueger et al. found that interview data could be used to model a comparable continuum. Their model comprised 110 items, and thus provided a potentially more comprehensive set of developmental stages.
