Decision-making about corticosteroids in relapses of multiple sclerosis - development of a questionnaire based on the theory of planned behaviour

Background: Relapses of multiple sclerosis are burdensome events and entail potentially lasting loss of function. People with multiple sclerosis have to consider corticosteroids, providing limited benefits and the risk of adverse effects. Objective: To develop and validate a questionnaire investigating the internal process of people with multiple sclerosis making decisions about corticosteroids. Methods: The questionnaire is structured by three domains, attitude, subjective social norm, and perceived behavioural control, which according to the theory of planned behaviour determine action planning. The development is inspired by a previous questionnaire studying decisions on immunotherapy. The questionnaire was tested in qualitative think-aloud interviews (n=10) for feasibility and comprehensibility and in an online survey (n=203) to assess construct and criterion validity. Results: The 18-item questionnaire was considered feasible and comprehensible. It predicted the intention to receive corticosteroids in up to 82.3% of cases. "Subjective social norm" impacted most on intention. The questionnaire also proved sensitive for autonomy preferences of people with multiple sclerosis. Conclusion: This study shows that the questionnaire appropriately explains the internal process people with multiple sclerosis run through when considering corticosteroids. It can be used to inform developments of tailored support for people with multiple sclerosis in making informed decisions about relapse management.