Development and validation of a scale to measure therapeutic misunderstanding with respect to clinical trial research participation

Clinical trial research participants often exhibit therapeutic misunderstanding. Factor and item analyses of responses by 464 community-dwelling older adults (age 49+) recruited online enabled the development of the 23-item Therapeutic Misunderstanding Scale (TMU). In accord with Horn and Grady’s three facets definition (2003), a three-factor structure was supported by both exploratory and confirmatory factor analyses (n = 164 & n = 300 respectively). Internal consistency of responses to the full TMU as well as the therapeutic misconception, misestimation, and optimism subscales was calculated as alpha = .90, alpha =.87, alpha =.79, and alpha =.75, respectively. Correlations between the TMU and related instruments by 37 clinical trial participants provide support for convergent and discriminant validity of responses to this scale. Test-retest reliability was found to be r = .54 over an average interval of 35 weeks. Results are discussed in context of ongoing challenges to define and measure therapeutic misunderstanding.