Development of Rasch-based short screenings for the assessment of treatment motivation in patients with cardiovascular diseases.

The aim of the study was to develop unidimensional test-fair and economic short screenings to assess treatment motivation in patients with cardiovascular diseases using the Rasch analysis. After pretesting for relevance and comprehension, a pool of 132 items on treatment motivation was completed by a sample consisting of 1168 patients with cardiovascular diseases recruited in two German cardiological rehabilitation centers. Confirmatory factor analyses and the Rasch analyses were conducted. The confirmatory factor analyses confirmed a three-factor structure of the treatment motivation construct with task self-efficacy, outcome expectancies and intention as factors. Using the Rasch analysis for each of the three factors and removing items with misfit, differential item functioning and local response dependency reduced the initial item pool to the three short screenings. The short screenings fit to the Rasch model with a root mean square error of approximation (RMSEA = 0.021 (task self-efficacy; seven items); RMSEA = 0.024 (outcome expectancies; 12 items), RMSEA = 0.027 (intention; nine items). Person-separation reliability was 0.81, 0.82, and 0.73. Unidimensionality could be verified. The calibrated, unidimensional short screenings provide a psychometrically sound option for an initial- and follow-up assessment of treatment motivation in rehabilitation patients with cardiovascular diseases. Further testing in other cardiovascular diseases populations is needed to increase generalizability.Implications for rehabilitationNew short screenings for the assessment of treatment motivation: task self-efficacy, outcome expectancies, intention in rehabilitation patients with cardiovascular diseases are available.Treatment motivation short screenings consist of seven items (treatment motivation short screening), 12 items (treatment motivation short screening), nine items (treatment motivation short screening) and are therefore especially timesaving.The short screenings demonstrate good psychometric properties, cover a wide spectrum of task self-efficacy, outcome expectancies and intention, and are free of local dependencies and of differential item functioning regarding to gender, age and cardiovascular diagnoses.Using a Rasch based unidimensional short screening is a test-fair and economic method to assess patients' treatment motivation, which might help to improve rehabilitation health care tailored to patients' needs.