Applying the theory of planned behaviour to multiple sclerosis patients' decisions on disease modifying therapy--questionnaire concept and validation.

Patients making important medical decisions need to evaluate complex information in the light of their own beliefs, attitudes and priorities. The process can be considered in terms of the theory of planned behaviour. Decision support technologies aim at helping patients making informed treatment choices. Instruments assessing informed choices need to include risk knowledge, attitude (towards therapy) and actual uptake. However, mechanisms by which decision support achieves its goals are poorly understood.Our aim was therefore to develop and validate an instrument modeling the process of multiple sclerosis (MS) patients' decision making about whether to undergo disease modifying (immuno-)therapies (DMT).