Development and psychometric properties of the general public's attitudes toward advance care directives scale in Portugal

Background: To date, no instrument in Portugal has evaluated the attitudes of the population about advance care directives. This paper describes the development and testing of the General Public’s Attitudes Toward Advance Care Directives (GPATACD) Scale. Design and Methods: Methodological study. The development of the instrument was based on a literature review, updated in 2018. Face and content validity were verified by an expert panel and piloted among six participants. Data were collected in an online survey of 1024 Portuguese adults. The obtained data were analyzed using Varimax rotation, while the reliability was evaluated by calculating Cronbach’s alpha. Results: The scale achieves good Item-Content Validity Index (I-CVI) values, between 0.89 and 1.00, and scale-CVI values of 0.91. A principal component analysis generated four dimensions with 26 items as a final scale, with overall Cronbach’s alpha of 0.848. Conclusions: The findings demonstrate that the scale is valid and reliable as a vehicle for assessment of the general public’s attitudes toward advance care directives.