Development and initial validation of the Therapeutic Misunderstanding Scale for use with clinical trials research participants.

Therapeutic misconception is evident when clinical trials participants conflate research and treatment, erroneously believing that every aspect of the research is intended to be for their direct benefit. We developed the 20-item Therapeutic Misunderstanding Scale (TMU) based on responses from 464 community-dwelling adults 50+ years of age (Study 1). A three-factor solution based on Horng and Grady's (2003) three-facets definition was identified using both exploratory and confirmatory factor analyses (EFA and CFA; these analyses were performed on separate samples). CFA results point to a second-order solution where each of Horng and Grady's three facets contribute significantly to the measurement of a higher-order therapeutic misunderstanding latent construct. Internal consistency of TMU responses (full scale) as well as the therapeutic misconception, misestimation, and optimism subscales were calculated as α = 0.88, α = 0.83, α = 0.79, and α = 0.75, respectively. These results were subsequently supported with responses from former clinical trials participants (Study 2). This TMU provides applied researchers a brief measure for use in future studies as well as a screening instrument for clinicians to more fully assess informed consent for participation in clinical trials research.