Symptom Attribution in Patients with Medically Unexplained Symptoms. A Scale Development and Validation Study.

Introduction: In the care of patients with medically unexplained physical symptoms (MUPS) it is important what they think about their symptoms. Objective: To validate the psychometric properties of a symptom attribution scale in patients with MUPS and to verify its reliability. Methods: A non-probabilistic sample of 400 male and female adult patients were interviewed in the outpatient services of a family medicine hospital, 200 with MUPS and 200 with a defined organic pathology. Each group was diagnosed with defined criteria, and a scale with content and construct validity was applied by means of principal component analysis with varimax rotation. Results: The scale was made up of 12 items with two factors, one of symptom psychosocial attribution and others with organic attribution. The psychosocial-origin factor showed a variance of 49.7%. The goodness-of-fit test demostrated that the correlation matrix was adequate, and Bartlett's sphericity test indicated statistical significance (p < 0.0001); Cronbach's alpha was 0.841. Conclusion. The scale showed acceptable construct validity and good reliability and stability. The implications of these results for future measurement research are discussed.