Measurement of shared decision making - a review of instruments

The last years have seen a clear move towards shared decision making (SDM) and increased patient involvement in many countries. However, as the field of SDM research is still relatively young, new instruments for the measurement of (shared) decision making (process, outcome and surrounding elements) are constantly being developed. Thus, the aims of this structured review were to give an update on current developments regarding the measurement in the field of SDM, as well as to give a short overview of published and unpublished instruments. We conducted an electronic literature search in PubMed and the Web of Science database, performed hand searches of relevant journals and contacted key authors in the field. We found eight scales that have been subjected to further psychometric testing, eleven new and psychometrically tested instruments and nine developments that are still in the publishing process. The results show that there is a trend towards measuring SDM processes from a dyadic approach (assessing both the patient's and the clinician's perspective). More and more scales have been developed and tested in languages other than English, which indicates the growing research efforts in various countries. While reliability of most scales is good, they differ in their extent of validation. Further psychometric testing is needed, as well as the development of a theoretical measurement framework in order to improve consistency of measured constructs across research groups.