Background: In rehabilitation, therapeutic alliance is regarded as a common therapeutic factor which is associated with improvements in clinical outcomes. The Working Alliance Inventory (WAI) measures therapeutic alliance and is frequently used in rehabilitation research, however it has not been validated for rehabilitation.
Objectives: To determine content validity (including face validity), internal consistency and construct validity of the Working Alliance Inventory Rehabilitation Dutch Version (WAI-ReD).
DesignObservational validation study.
Methods. In phase 1 content and face validity of the WAI-ReD was judged by professionals (n= 15) and in phase 2 by patients (n= 22). In phase 3, 14 hypotheses were tested in patients (n=138) regarding content validity (missing items, floor and ceiling effects), internal consistency and construct validity (factor structural testing, correlations WAI-ReD with Session Rating Scale (SRS), the Helping Alliance Questionnaire II (HAQ-II) and Visual Analog Scale of Pain (VASpain)). Differences between gender, age and type of therapists were tested.
Results: After phase 1 and phase 2 the WAI-ReD was formulated. Regarding content validity, missing items were negligible and ceiling effects were present in all items. Regarding internal consistency, Cronbach’s α ranged between 0.804 and 0.927. Regarding construct validity, correlations between WAI-ReD, SRS, HAQ-II and VASpain fell within the hypothesized ranges. No effects of gender and age were found. Differences were found in scores of patients treated by different types of therapists. Eleven of 14 hypotheses were confirmed.
Limitations: Ceiling effects were present in all items, ceiling effects may affect the responsiveness of the WAI-ReD.
Conclusions: The WAI-ReD has moderate content validity, strong internal consistency and strong construct validity.