The psychometric characteristics of an assessment instrument for perceived harmfulness in adolescents with musculoskeletal pain (PHODA-youth).

Background: Cognitive-behavioural models of chronic pain predict that dysfunctional assumptions about harmfulness of activities may maintain pain-related fear and disability. To assess perceived harmfulness in adolescents, the Photograph Series of Daily Activities for youth (PHODA-youth) was developed. Information concerning its methodological quality is currently lacking.
Objective: To investigate psychometric characteristics (factor structure, test-retest reliability, construct validity) and feasibility of the PHODA-youth in adolescents with chronic musculoskeletal pain.
Study Design: Test-retest design.
Study Population: Adolescents aged 13-21 years with chronic nonspecific musculoskeletal pain.
Methods: Participants filled in an electronic version of the PHODA-youth including 89 items twice with a 4-week interval. The instrument's factor structure was determined by a factor analysis. Construct validity was studied with criterion variables: catastrophizing (Pain Catastrophizing Scale for Children), pain intensity (visual analogue scale), depression (Children's Depression Inventory) and pain-related disability (Functional Disability Inventory) using regression analysis. Test-retest reliability was evaluated based on the Pearson correlation coefficient. Feasibility was studied with self-constructed questions.
Results: Seventy-one adolescents participated. Results show a three-factor structure for the PHODA-youth including 51 items with subscales labelled as: 'activities of daily life', 'intensive physical activities' and 'social activities'. Total and subscale scores showed a high internal consistency. Its test-retest reliability was good (r = 0.94) and its construct validity is supported by the finding that both catastrophizing (β = 0.25; p = 0.02) and disability (β = 0.71; p < 0.001) were uniquely related to the PHODA-youth. In addition, feasibility appeared adequate.
Conclusion: The findings support the PHODA-youth as a valid and reliable measure of the perceived harmfulness of activities in adolescents with musculoskeletal pain.
(© 2014 European Pain Federation - EFIC®)