Healthy subjects volunteering for Phase I studies: influence of curiosity, exploratory tendencies and perceived self-efficacy.

OBJECTIVE To test the hypothesis that trait-curiosity and perceived self-efficacy influence the willingness of healthy subjects to volunteer for participation in Phase I studies. MATERIALS AND METHODS A group of healthy subjects who had never participated in clinical studies ("index group") were invited to participate in a Phase I study. They were assessed with regard to trait curiosity (Curiosity and Exploration Inventory; CEI-T) and perceived self-efficacy (Self-Efficacy Scale; SES) and subjects who accepted the invitation to participate were compared with those who refused and with a group of healthy subjects who had previously participated in clinical studies ("validation group"). RESULTS A significant positive correlation was found between the willingness to participate and the CEI-T total score (R=0.28; p<0.01), exploratory tendencies (R=0.34; p<0.001), SES total score (R=0.30, p<0.01), initiative and persistence (R=0.29, p<0.01), planning/goal setting (R=0.19, p<0.05) and social self-efficacy (R=0.29; p<0.01). The "index group" subjects who accepted the invitation to participate showed significantly greater CEI-T exploratory tendencies (Z=-3.334, p = 0.001, Mann-Whitney test) and total scores (Z=-2.703, p<0.01) and greater SES total score (Z=-3.131, p<0.01), initiative and persistence (Z=-3.065, p<0.01), planning/goal setting (Z=-2.173, p<0.05) and social self-efficacy (Z=-2.954, p<0.01) than subjects who refused. No differences were found between the subjects in the "index group" who accepted the invitation and subjects in the "validation group". Using a logistic regression model, both CEI-T exploratory tendencies and SES initiative/persistence were significant predictors of participation. CONCLUSION Subjects higher in curiosity/exploration and in perceived initiative/persistence are more willing to volunteer for Phase I studies. The impact of these self-selection biases on Phase I study results is unknown but deserves further evaluation.