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

Background and Purpose 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). Methods 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. Results 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. Discussion 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.