Developing the First Validity of Shared Medical Decision-Making Questionnaire in Taiwan

Abstract

Due to a lack of valid Taiwanese instruments measuring Shared Medical Decision-making (SMDM) in Taiwan. The purpose of the study is to investigate the reliability and validity of the Shared Medical Decision-making process. Total 350 patients were randomly recruited from a medical centre in Taiwan. As a theoretical basis steps of the SMDM process were defined in an expert panel. Item formulation was then conducted according to the Delphi method and a pool of 16 items was constructed. In addition, the Winstep software was used to examine whether the data fit Rasch test model. Items with outfit or infit MNSQs (mean square errors) not in the range between 0.77 and 1.30 are usually deemed as potential misfits. Successive Rasch analyses were performed until a final set of items was obtained. After eliminating 1 item the remaining 15 form a unidimensional scale with an acceptable reliability for person measures 0.77 and very good reliability for item difficulties 0.97. Analysis of subgroups revealed a different use of items in different conditions. Taiwanese Shared Medical Decision-making Questionnaire (SMDMQ) is a 15 items normative instrument. In addition, a theory-driven instrument to measure the process of SMDM has been developed and validated by use of a rigorous method revealing first promising results. Yet the ceiling effects require the addition of more discriminating items, and the different use of items in different conditions demands an in depth analysis.