DEVELOPING THE FIRST VALIDATION OF THE SHARED DECISION-MAKING QUESTIONNAIRE IN TAIWAN

Purpose: Evidence based patient choice seems based on a strong liberal individualist interpretation of patient autonomy. Due to a lack of valid Taiwanese instruments measuring shared decision-making (SDM). The purpose of the study is to investigate the reliability and validity of the SDM process in Taiwan.

Methods: As a theoretical basis steps of the SDM process were defined in an expert panel. Item formulation was then conducted according to the Delphi method and a pool of 25 items was constructed. In addition, the Winsteps software was used to examine whether the data fit Rasch model and match a single construct. Items with outfit or infit MNSQ (mean square error) not in the range between 0.06 and 1.4 are usually deemed as potential misfits to the Rasch model and considered for deletion from the assessment sequence. Successive Rasch analyses were performed until a final set of items was obtained that met the model’s fit requirements.

Results: A convenience sample of 250 patients recruited from ChungShan university hospital. The average age of the subjects is 34.68 years old. There are 129 male (51.6%). Among them, 52.8% are married. After eliminating 4 items the remaining 21 form a unidimensional scale with an acceptable reliability for person measures (0.86) and very good reliability for item difficulties (0.98). The result showed that the questionnaire consisted of four scales. Two of the scales reflected the concepts of patient autonomy and consumerist poles of the liberal individualist, one scale reflected control preferences and of procedural independence, and the fourth scale reflected ideals of risk information communication. Analysis of subgroups revealed a different use of items in different conditions. Furthermore the scale showed high ceiling effects.

Conclusions: The Shared Decision-making Scale is a 21 item normative instrument. In addition, a theory-driven instrument to measure the process of SDM 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.