The aim is to familiarize physicians and researchers with the most important concepts of item response theory (IRT) and with its usefulness for improving test administration and data collection in health care. Special attention is given to the versatility of its use within the rheumatic field.
This short tutorial describes the most important basic principles of item response theory, including the underlying assumptions, the model parameters, and the different models that can be applied. Practical applications are discussed to demonstrate the potential utility of IRT within clinical practice.
IRT has proven to be useful for the development and evaluation of both clinical measures as well as patient reported outcomes used for measuring health status in observational studies and clinical trials. Promising features of IRT for the future of test administration are the assessment of local reliability and differential item functioning, the cross-cultural validation or equation of instruments, the development of large item banks, and the administration of computerised adaptive tests. These modern techniques have the ability to maximise measurement precision while simultaneously minimise response burden.
IRT provides a theoretical basis for developing alternatives to the existing tools for assessing health outcome measures in rheumatology.