The 9-item Shared Decision Making Questionnaire (SDM-Q-9). Development and psychometric properties in a primary care sample

Objective: To develop and psychometrically test a brief patient-report instrument for measuring Shared Decision Making (SDM) in clinical encounters.

Methods: We revised an existing instrument (Shared Decision Making Questionnaire; SDM-Q), including the generation of new items and changing the response format. A 9-item version (SDM-Q-9) was developed and tested in a German primary care sample of 2351 patients via face validity ratings, investigation of acceptance, as well as factor and reliability analysis. Findings were cross-validated in a randomly selected subsample.

Results: The SDM-Q-9 showed face validity and high acceptance. Factor analysis revealed a clearly one-dimensional nature of the underlying construct. Both item difficulties and discrimination indices proved to be appropriate. Internal consistency yielded a Cronbach's alpha of 0.938 in the test sample.

Conclusion: The SDM-Q-9 is a reliable and well accepted instrument. Generalizability of the findings is limited by the elderly sample living in rural areas of Germany. While the current results are promising, further testing of criterion validity and administration in other populations is necessary.

Practice implications: The SDM-Q-9 can be used in studies investigating the effectiveness of interventions aimed at the implementation of SDM and as a quality indicator in health services assessments.