IRTPRO (Item Response Theory for Patient-Reported Outcomes) is an entirely new application for item
calibration and test scoring using IRT. IRTPRO implements algorithms for maximum likelihood estimation of item parameters (item calibration) for several unidimensional and multidimensional item response theory (IRT) models for dichotomous and polytomous item responses. In addition, the software provides computation of goodness-of-fit indices, statistics for the diagnosis of local dependence and for the detection of differential item functioning (DIF), and IRT scaled scores. This paper illustrates the use, and some capabilities, of the software.