Development of the myositis activities profile--validity and reliability of a self-administered questionnaire to assess activity limitations in patients with polymyositis/dermatomyositis.


OBJECTIVE To develop a disease-specific questionnaire for assessing limitations in activities of daily life, the Myositis Activities Profile (MAP), and to investigate its validity and reliability. METHODS Groups of 10, 27, 31, and 17 patients with polymyositis (PM) or dermatomyositis (DM) participated in different parts of the study. In the first draft of the MAP, patients rated their difficulty and experienced importance of selected activities from the International Classification of Impairments, Disabilities, and Handicaps (ICIDH)-2 Beta-2 draft. The 37 highest rated activities formed a second draft of the MAP, which was analyzed for internal redundancy and consistency. For construct validity a third draft was correlated with CPK levels, the Functional Index in myositis (FI), the Arthritis Impact Measurement Scales-2 (AIMS2), the Health Assessment Questionnaire (HAQ), and subjective global disease impact. Test-retest reliability over one week was investigated. RESULTS There were several expected correlations (rs > 0.50) between subscales of the MAP and corresponding subscales of the AIMS2, and a 31 item MAP correlated moderately with the HAQ (rs = 0.70) and less with the FI (rs = 0.55), subjective global disease impact (rs = 0.43), and CPK levels (rs = 0.17). No systematic differences were found between test and retest, and weighted kappa coefficients ranged from Kw = 0.56 to 0.77. CONCLUSION The MAP seems to be a valid and reliable method for assessing activity limitations in patients with PM and DM.