This study aimed to measure the psychometrics qualities of an extended model of the Theory of Planned Behavior (TPB) applied to plasma donation, and its relevance in the evaluation of interventions aiming at converting whole-blood donors (WBD) to plasma donation.

Two studies were conducted. The first (N = 433) compared the efficacy of two communication strategies (standard strategy centered on motivations to donate vs. experimental strategy centered on barriers to donate) for influencing specific determinants of the extended model of the TPB and for engaging WBD in plasma donation. The second study (N = 309) evaluated the gain of adding to the experimental strategy an implementation intentions protocol to facilitate the behavior.

Study 1 showed the relevance of the extended model as a measurement tool of intention’s determinants, and the efficacy of the experimental strategy compared to the standard approach to bolster intention, F(2,430) = 7.03, p < 0.001, partial η² = 0.032, and to increase the likelihood of commitments χ2(2, N = 433) = 11.904, p = 0.003, Cramer’s V = 0.17. Study 2 replicated these results but did not demonstrate any effect of the implementation intentions protocol to strengthen the intervention, χ²(1, N = 188) = 1.341, p = 0.25.

These studies showed that addressing barriers to donation is an efficient communication and recruitment strategy. We encourage blood collection agencies to develop communication campaigns in this direction rather than focusing on donors motivations.