PURPOSE: Establishing construct validity of the ACS-NL in individuals with Parkinson's disease (PD).

METHOD: Discriminative validity was established in 191 community-dwelling individuals with PD using an extreme groups design (Hoehn and Yahr stages 1 and 3). Convergent validity was determined by relating the performance scores of the ACS-NL to the scores of the Canadian Occupational Performance Measure (COPM) and the Parkinson's Disease Questionnaire (PDQ-39) scores, and relating ACS-NL satisfaction scores to the COPM scores and to the Utrecht Scale for Evaluation of Rehabilitation Participation (USER-P).

RESULTS: The ACS-NL discriminated between individuals with PD with H&Y stages 1 and 3 (U = 524.5, Z = -5.453). ACS-NL performance scores correlated weakly with COPM scores (r = (0).19) and moderately with PDQ-39 scores (r = 0.44-0.55). The ACS-NL satisfaction scores correlated weakly with COPM scores (r = 0.23), and moderately with USER-P scores (r ≥ 0.40).

CONCLUSIONS: This study contributed to the validation of the ACS-NL. The assessment enhances the possibility of monitoring participation in activities in individuals with PD. Implications for Rehabilitation The ACS-NL appears to hold good potential for use in the assessment of participation in activities in individuals with PD. The ACS-NL has added value parallel to administration of other instruments measuring participation (COPM) and quality of life (PDQ-39). This study demonstrates the capacity of the ACS to measure a unique construct of participation and helps to improve the psychometric properties and administration of the ACS-NL in practice.