Validating patient and physician versions of the shared decision making questionnaire in oncology setting

Background: This study investigated the psychometric properties of the 9Item Shared DecisionMaking Questionnaire (SDMQ9) and the 9Item Shared DecisionMaking Questionnaire–Physician version (SDMQDoc) using comprehensive and thorough psychometric methods in an oncology setting. Methods: Cancer survivors (n=1783; 928 [52.05%] males) and physicians (n=154; 121[78.58%] males) participated in this study. Each cancer survivor completed the SDMQ9. Physicians completed the SDMQDoc for each of their cancer patient. Confirmatory factor analysis (CFA) and Rasch model were used to test the psychometric properties of SDMQ9 and SDMQDoc. Results: SDMQ9 and SDMQDoc demonstrated unidimensional structure in CFA and Rasch model. In addition, the measurement invariance was supported for both SDMQ9 and SDMQDoc across sex using the multigroup CFA. Rash analysis indicates no differential item functioning(DIF)across sex for all the SDMQ9 and SDMQDoc items. SDMQ9 and SDMQDoc were moderately correlated (r=0.41; P lt;0.001). Conclusion: SDMQ9 and SDMQDoc are valid instruments to assess shared decision making in the oncology setting.