Severity threshold parameters representing the relative severity of each AUD criterion along a continuum of the latent trait of alcohol use disorder, with larger parameters reflecting greater severity, were estimated from a two-parameter logistic model using item response theory (IRT) models (see Section 2.4, Analysis). These parameters are directly proportional to the frequency with which the criteria were endorsed and correspond to the b parameters from the model. (The a parameters, which measure the ability of the criteria to discriminate people who are higher and lower on the continuum of severity, were not used in this analysis.) A weighted severity score (range = 0 to 26.07) was calculated by summing the values of the severity threshold parameters across all positively endorsed criteria.
