Psychometric properties of the Impact on Participation and Autonomy Questionnaire.

OBJECTIVE To examine the homogeneity, test-retest reliability, construct validity, and concurrent validity of the Impact on Participation and Autonomy Questionnaire (IPAQ). DESIGN Cross-sectional study with a test-retest subsample. PATIENTS One hundred twenty-six persons from 5 diagnostic groups recruited from the outpatients clinics of 2 rehabilitation centers and the rehabilitation department of an academic hospital. INTERVENTIONS The IPAQ and 3 other self-administered questionnaires (Sickness Impact Profile [68-item version], London Handicap Scale [LHS], Medical Outcome Study Short-Form Health Survey). The IPAQ was completed twice by 75 respondents within approximately 2 weeks. RESULTS The IPAQ addresses autonomy and participation in 5 domains: autonomy indoors, family role, autonomy outdoors, social relations, and work and educational opportunities. Cronbach's alpha for the several domains ranged between.81 and.91, indicating good homogeneity. On item level, weighted kappas ranged between.56 and.90. On domain level, the test-retest reliability of the IPAQ was good: intraclass correlation coefficients ranged between.83 and.91. Convergent validity was largely supported by the correlations between 4 domains of the LHS and the IPAQ. Discriminant validity was best demonstrated by low correlations between the IPAQ and 2 domains of the LHS representing theoretically different constructs. CONCLUSION The IPAQ is a reliable and valid instrument for assessing autonomy and participation in chronic disorders. Its responsiveness requires further study.