Validity and reliability of the instrument Performance and Satisfaction in Activities of Daily Living (PS-ADL) and its clinical applicability to adults with rheumatoid arthritis

Aim: This study set out to evaluate the validity and reliability of the instrument Performance and Satisfaction of Activities of Daily Living (PS-ADL) in patients with rheumatoid arthritis (RA). The PS-ADL is a questionnaire including 39 actions divided into 12 activities measuring the degree of difficulty and satisfaction with activity performance. Method: Construct validity was examined by factor analysis. For convergent and discriminant validity evaluation, the Performance and the Satisfaction scales were correlated to the Health Assessment Questionnaire (HAG, the Rheumatoid Arthritis Self-Conception (RASC), pain, fatigue, and mobility. Internal consistency was tested and repeated measurements were taken to establish the Percentage Agreement (PA) and correlation coefficients for test-retest reliability. Results: The factor analysis revealed the PS-ADL scale to be unidimensional. Significant correlations were seen between the Performance and Satisfaction scales and the HAQ (r(s) 0.78, 0.67), and between the RASC and Satisfaction scale (r(s) 0.45). Cronbach's alpha level ranged from 0.41 to 0.92 for the Performance scale and 0.66 to 0.94 for the Satisfaction scale. The percentage agreement (PA) at action level ranged from 68% to 91% for the Performance scale and from 59% to 91% for the Satisfaction scale. Conclusion: The PS-ADL is a valid instrument with satisfactory reliability. It is easy to handle and can be recommended for use in RA patients.