The growth and development of psychology and mental healthcare is accompanied by a rapid increase in the number of assessment instruments that are utilizer. The downside of presented variety and...Show moreThe growth and development of psychology and mental healthcare is accompanied by a rapid increase in the number of assessment instruments that are utilizer. The downside of presented variety and availability is an abundance, which hinders interpretation of test results, comparison of outcomes, and communication among colleagues and with patients about their test results. This may lead to diminished patient involvement and treatment progress. A common metric is lacking, linking test scores to a common metric, such as the T-score metric based on the Item Response Theory (IRT), may provide a solution to the Babel tower dilemma. The current study investigates the feasibility of an approach to develop a common metric and applies this to three anxiety-related questionnaires: Agoraphobic Cognitions Questionnaire (ACQ), Bodily Sensations Questionnaire (BSQ), and Mobility Inventory (MI) based on the data collected from 210 patients and 430 normal participants. IRT was applied to attain T-scores, form non-linear transformation formulas to estimate T-scores based on raw test scores and theory-based T-scores. The distributions and correspondence of the two Tscores were inspected. The theory-based T-scores and T-scores based on transformation formulas correspond sufficiently for ACQ and BSQ, but for the MI the proposed approach failed to produce useable T-scores. The reasons, pros and cons of IRT are discussed, as well as practical applications, focusing the attention on Routine Outcome Monitoring (ROM). The use of a common metric will allow ease comparison of scores from various instruments and aids communication, while characteristics of IRT allow the use of variable questionnaires and adaptive tailored testing assisting the utilization of ROM in treatment.Show less