Testing psychometric properties of Shared Decision Making Questionnaire - Physician Version (SDM-Q-Doc) in an Italian real-world psychiatric clinical sample

Abstract

Objectives: The Shared Decision Making Questionnaire-Physician Version (SDM-Q-Doc) is the main tool assessing SDM relationship between patient and physician using the clinician viewpoint. It is reliable in all medical fields, and the validation of its Italian version was still missing. Our aim was to validate the Italian version of the SDM-Q-Doc in a clinical sample of patients suffering from severe mental illness.

Methods: We approached 369 patients affected by major psychiatric disorders (including schizophrenia spectrum disorders, affective disorders and eating disorders) in a real-world outpatient clinical setting. We run the Confirmatory Factor Analysis (CFA) to test the SDM-Q-Doc structure. We calculated the correlations between the SDM-Q-Doc and the Observing Patient Involvement (OPTION) scale, used as comparing test, and McDonald ω coefficient to measure convergent validity and internal consistency respectively.

Results: We reached a response rate of 93.2% (344 final participants). The CFA showed a very good fit compared of the Italian version of SDM-Q-Doc (χ2/df=3.2, CFI=.99, TLI=.99, RMSEA=.08, SRMR=.04). We found several correlations between the SDM-Q-Doc and OPTION scale supporting a robust SDM-Q-Doc construct validity, while internal consistency of the scale was McDonald ω coefficient .92. Further, inter-item correlations ranged from .390 to .703, with a mean of .556.

Conclusions: This study confirms the suitability of the Italian version of SDM-Q-Doc, with good reliability and soundness even when compared to other languages validated versions and to OPTION scale. SDM-Q-Doc represents an easy-to-use physician-centered measure to assess patients' involvement in medical decision-making, well performing in the Italian-speaking population.