Measuring improvement in health-status with the Oxford Participation and Activities Questionnaire (Ox-PAQ).

Background: The Oxford Participation and Activities Questionnaire (Ox-PAQ) is a recently validated 23-item generic patient reported outcome measure that is theoretically grounded in the World Health Organisation International Classification of Functioning, Disability and Health (ICF), as well as fully FDA compliant. The measure comprises three domains, Routine Activities (14 items), Emotional Well-Being (5 items) and Social Engagement (4 items), and has been shown to be both valid and reliable. The aim of this study was to make a preliminary assessment of the sensitivity to the change of the Ox-PAQ. Methods: Three hundred and seventy three people with either chronic pulmonary obstructive disease, motor neurone disease, multiple sclerosis or Parkinson’s disease completed the Ox-PAQ electronically on two occasions, six months apart. Participants completed an additional four questions during the second administration of the Ox-PAQ in order to assess any relevant changes since baseline. For each of the three Ox-PAQ domains, the minimally important difference (MID) and effect size (ES) was calculated from those participants indicating small, but meaningful positive improvement. Results: Two hundred and ninety respondents were entered into the final analysis, 77.74% of the original sample. For those indicating “slight improvement” in Routine Activities (n=19), an MID of 7.51 and an ES of 0.32 was calculated. For Emotional Well-Being (n=26), the MID was 10.77 and the ES 0.44. For Social Engagement (n=16), the MID was 5.47 and the ES 0.28. Conclusion: Data presented provides MID improvement and effect sizes for Ox-PAQ domains that will act as preliminary guidance for those powering clinical trials assessing activity and participation. Future research with larger samples will provide further sensitivity to change data for the Ox-PAQ.