Development and Validation of the AdT-Physio Scale: A Tool to Assess Adherence and Perception of Physical Therapist Intervention in Patients With Cystic Fibrosis

Objective The purpose of this study was to develop a scale to measure patient adherence to physical therapist intervention and to report psychometric properties in patients with cystic fibrosis (CF). Methods This observational, multicenter, qualitative, and cross-sectional study was divided into 2 phases: development of scale items (content validity) and assessment of psychometric properties (construct validity, reliability, and convergent/discriminant validity). Recruited were 121 patients with CF (aged ≥16 years). Sociodemographic characteristics, lung function testing, Coping with Stress Self-Efficacy, brief Coping Orientation to Problems Experienced inventory, and the scale of Adherence to Treatment of Physiotherapy (AdT-Physio) scale were evaluated. Results The final version of the AdT-Physio scale consists of 15 items distributed across 2 subscales: compliance and beliefs about treatment/therapist. The scale showed high internal consistency (Cronbach α = .897; 95% CI = 0.868–0.922) and subscales above 0.800. The 2-factor confirmatory factor analysis model fitted the data reasonably well: χ2 (76) = 111.96, comparative fit index = 0.982, Tucker-Lewis index = 0.978, root mean square error of approximation = 0.063, 95% CI = 0.036 to 0.086, and weighted root mean square residual = 0.720. No floor or ceiling effects were identified. There was a positive, significant, and moderate-low magnitude correlation with the total Coping Orientation to Problems Experienced inventory (r = .360) and Coping with Stress Self-Efficacy subscale efficacy expectations scores (r = .304). For discriminant validity, there was a positive, significant, and moderate correlation between the total and the age of the patients (r = .354). Conclusions The AdT-Physio scale is psychometrically valid and reliable for use in the clinic for the assessment of adherence to physical therapy in patients with CF. Impact Ultimately, the authors propose this documentary instrument to assess the evaluation of the therapeutic alliance in a valid and objective manner. The AdT-Physio scale provides us with a greater degree of understanding of the problems behind noncompliance with treatment to advance person-centered decisions in physical therapy and thereby enhance the effectiveness of care.