Psychometric properties of a new treatment expectation scale in rheumatoid arthritis: an application of item response theory

摘要

Patient-generated health outcome measures are important in the assessment of long-term treatment goals for Rheumatoid Arthritis (RA), but few psychometrically sound measures are available. The MAPLe-RA (Measuring Actual Patient-Led expectations in RA) is a new questionnaire and its psychometric properties are not investigated. This study aims to examine these properties for each of the items using Item Response Theory (IRT)?. Participants were included if they completed the scale (MAPLe-RA). A one parameter (Rasch) model and a two parameter logistic (2PL) model were applied to these data using M-plus software. One hundred thirty-eight patients with RA were included in the analysis. MAPLe-RA scale comprised of 21 items, the mean score was 71 (20.28) ranging from 0 to 105. Most items operated in the high expectations part of the items characteristics curves (ICC). Item discrimination varied widely, items with the highest discrimination capacity from the three domains were: pain (physical domain); control of my RA (self-management) and maintaining social role (psycho-social domain); feeling better overall and involvement in treatment decision making (impact of new treatment domain). RA patients’ expectations of treatment are higher in the physical and psycho-social domains and less so in the impact of new treatment domain.