Development and Validation of the WAI-Tele-Reha-G: A Measure of Therapeutic Alliance in Telerehabilitation

Therapeutic alliance (TA)-the collaborative therapist-client partnership-is pivotal to outcomes, yet TA tools tailored to telerehabilitation are limited. We developed and preliminarily validated a therapist-reported measure for physiotherapists (PTs), occupational therapists (OTs), and speech and language therapists (SLTs): the Working Alliance Inventory-Telerehabilitation (WAI-Tele-Reha-G).

Items drew on expert interviews, adaptation guidelines, and the German WAI-Short Revised (therapist version) and were refined via cognitive interviews (n = 9) and pilot testing (n = 34). Validation involved German-speaking PTs, OTs, and SLTs (test: n = 128; retest: n = 84). Rasch partial credit modelling assessed model fit, unidimensionality, local independence, threshold ordering, and differential item functioning (DIF). Reliability (Cronbach's alpha, Person Separation Index [PSI]), test-retest reliability (Lin's concordance correlation coefficient [CCC]), convergent validity (with the Unified Theory of Acceptance and Use of Technology-2 Questionnaire [UTAUT-2], Technology Commitment-Short Scale, 5-item Revised Vocational Self-Efficacy Scale), known-groups validity, and targeting were evaluated.

Goal, task and bond scales generally fit the Rasch model and were unidimensional with ordered thresholds; no DIF was detected in this sample. Minor local dependence in the task scale was handled via a superitem during Rasch estimation; scoring remained at the item level. Internal consistency was good (alpha = 0.80-0.81) and PSI modest (0.72-0.74). Test-retest reliability was excellent (CCC = 0.81-0.93). Correlations among goal, task, and bond were moderate-to-strong; correlations with technology acceptance/commitment and vocational self-efficacy were low-to-moderate, as hypothesised. Ceiling effects were < 15%, with targeting skewed towards higher TA levels.

The WAI-Tele-Reha-G shows preliminary evidence of satisfactory psychometric properties for a therapist-reported assessment of TA in telerehabilitation. Interpretation should consider the modest sample, therapist-only perspective, targeting skew, and Rasch adjustments. Future work should add more challenging items to improve discrimination at high TA levels and develop a patient-reported version to capture the dyadic nature of TA.