Item response theory has its origins in educational measurement and is now commonly applied in health-related measurement of latent traits, such as function and symptoms. This application is due, in large part, to gains in the precision of measurement attributable to item response theory and corresponding decreases in response burden, study costs, and study duration. The purpose of this paper is twofold: introduce basic concepts of item response theory and demonstrate this analytic approach in a worked example, a Rasch model (1PL) analysis of the Eating Assessment Tool (EAT-10), a commonly used measure for oropharyngeal dysphagia. The results of the analysis were largely concordant with previous studies of the EAT-10 and illustrate for brain impairment clinicians and researchers how IRT analysis can yield greater precision of measurement.

The past 20 years have seen the development of instruments designed to specify standards and evaluate the adequacy of published studies with respect to the quality of study design, the quality of findings, as well as the quality of their reporting. In the field of psychometrics, the first minimum set of standards for the review of psychometric instruments was published in 1996 by the Scientific Advisory Committee of the Medical Outcomes Trust. Since then, a number of tools have been developed with similar aims. The present paper reviews basic psychometric properties (reliability, validity and responsiveness), compares six tools developed for the critical appraisal of psychometric studies and provides a worked example of using the COSMIN checklist, Terwee-m statistical quality criteria, and the levels of evidence synthesis using the method of Schellingerhout and colleagues (2012). This paper will aid users and reviewers of questionnaires in the quality appraisal and selection of appropriate instruments by presenting available assessment tools, their characteristics and utility.