The Oxford Participation and Activities Questionnaire (Ox-PAQ): development of a short form and index measure

BACKGROUND: The Oxford Participation and Activities Questionnaire (Ox-PAQ) is a 23-item patient-reported outcome measure (PROM) theoretically grounded in the World Health Organisation International Classification of Functioning, Disability and Health. Initial validation of the Ox-PAQ identified three domains; routine activities (14 items), emotional well-being (5 items) and social engagement (4 items). The purpose of the analyses reported here were to determine whether an overall index score can be calculated from the measure, and then to determine whether a shorter form measure can replicate results on the index score. METHODS: Two surveys of people with long term conditions were undertaken. In the first study, higher order factor analysis is used to determine that a single index score can be calculated for the Ox-PAQ. Regression analyses are used to determine a sub-set of items selected for the Short Form Ox-PAQ (SF-Ox-PAQ). In the second study, results on the Ox-PAQ Single Index and SF-Ox-PAQ Single Index are compared with results from another generic measure, the EuroQol EQ-5D-5l. RESULTS: Higher order factor analysis confirmed that a single index score can be created from the Ox-PAQ. Further, linear regression indicated 14 items could reliably and accurately produce this index. The two methods of creating the index were highly correlated (ICC =0.99). The two indices were found to provide almost identical levels of correlation with EQ-5D-5L scores. CONCLUSION: Results indicate that the Ox-PAQ can be summed to provide an index score, and, furthermore, a sub set of fourteen items can very closely replicate the results gained from the original parent form.