Item response theory analyses of the parent and teacher ratings of the DSM-IV ADHD rating scale

The graded response model (GRM), which is based on item response theory (IRT), was used to evaluate the psychometric properties of the inattention and hyperactivity/impulsivity symptoms in an ADHD rating scale. To accomplish this, parents and teachers completed the DSM-IV ADHD Rating Scale (DARS; Gomez et al., Journal of Child Psychology and Psychiatry, 40, 265-274, 1999) for a group of 1,475 primary school-aged children. The results for the discrimination parameters showed that all symptoms for both groups of respondents were generally good for discriminating their respective latent traits. For virtually all symptoms, their threshold values showed moderate to large increases in the level of the latent trait at each subsequent response dichotomy, with the symptoms being especially good at representing the appropriate traits from mean to moderately high trait levels. The item information function values for most symptoms indicated reasonable reliability from, approximately, the mean trait levels to moderately high trait levels. These findings indicate good psychometric properties for the parent and teacher ratings of the DARS. The implications of the findings for the use of the DARS and other similar scales are discussed.