Social participation in older adults with joint pain and comorbidity; testing the measurement properties of the Dutch Keele Assessment of Participation

OBJECTIVE The Keele Assessment of Participation (KAP) questionnaire measures person-perceived participation in 11 aspects of life. Participation allows fulfilment of valued life activities and social roles, which are important to older adults. Since we aimed to use the KAP in a larger Dutch cohort, we examined the measurement properties of KAP in a Dutch sample of older adults with joint pain and comorbidity. DESIGN Cohort study. SETTING A community-based sample in Amsterdam, the Netherlands and North Staffordshire, UK. PARTICIPANTS Participants were aged 65 years and over, had at least two chronic diseases (identified through general practice consultation) and reported joint pain on most days (questionnaire). The Dutch cohort provided baseline data (n=407), follow-up data at 6 months (n=364) and test-retest data 2 weeks after 6 months (n=122). The UK cohort provided comparable data (n=404). OUTCOME MEASURES The primary outcome was person-perceived participation, as measured with the KAP. The measurement properties examined were the following: structural validity (factor analysis), internal consistency (Cronbach's α), reliability (intraclass correlation coefficients; ICC), construct validity (hypothesis testing), responsiveness (hypothesis testing and area under the curve) and cross-cultural validity (differential item functioning; DIF). RESULTS Factor analysis revealed two domains: KAPd1: 'participation in basic activities' and KAPd2: 'participation in complex activities', with Cronbach's α of 0.74 and 0.57 and moderate test-retest reliability: ICC of 0.63 and 0.57, respectively. Further analyses of KAPd1 showed poor construct validity and responsiveness. Despite the uniform DIF in item 'interpersonal relations', the total KAPd1 score seemed comparable between the Dutch and UK sample. CONCLUSIONS Only KAP domain 'participation in basic activities' showed good internal consistency and sufficient reliability. KAPd2 lacks sufficient measurement properties for application in studies, although items may be used as single items. Further development of the concept 'participation' may help the development and validation of instruments to measure participation.