Background: High patient participation in clinical research reduces selection bias, and ensures the generalisability of study findings. We explored study-related factors that may influence patients’ willingness to participate in research.

Methods: We submitted by mail two vignettes that described clinical research studies – a drug trial, and a diagnostic study – to patients recently discharged from hospital, and assessed

Background: High patient participation in clinical research reduces selection bias, and ensures the generalisability of study findings. We explored study-related factors that may influence patients’ willingness to participate in research.

Methods: We submitted by mail two vignettes that described clinical research studies – a drug trial, and a diagnostic study – to patients recently discharged from hospital, and assessed their willingness to participate. We used a factorial design to randomly allocate three study attributes per vignette: in the drug trial, presumed superiority of new drug versus equipoise, public versus industry funding, and random versus non-random treatment allocation; in the diagnostic study, common versus rare disease, genetic versus protein analysis, and automatic reporting of results versus reporting on demand.

Results: Of 2600 patients contacted, 1140 (44%) participated. Globally, willingness to participate in a drug trial was lower than in a diagnostic study (44.8% vs. 76.2%; P <0.001). In the drug trial, participation was significantly higher when the new drug was presented as presumably better than the old (vs. equipoise) and when the study was funded by public sources (vs. industry), but was not affected by the allocation method. None of the factors tested in the diagnostic study was associated with participation.

Conclusions: Patients were more likely to participate in a hypothetical observational diagnostic study than in a hypothetical drug trial. Participation in the trial was lower when clinical equipoise was expressed, and when the trial was funded by industry. These results suggest that some features of study design can influence participation.their willingness to participate. We used a factorial design to randomly allocate three study attributes per vignette: in the drug trial, presumed superiority of new drug versus equipoise, public versus industry funding, and random versus non-random treatment allocation; in the diagnostic study, common versus rare disease, genetic versus protein analysis, and automatic reporting of results versus reporting on demand.

Initially, we collected the participant responses in a paper case report form (questionnaire). These questionnaires were then recorded manually in a database by two independent persons (double entry) using pre-formatted variables. The database was finally imported in a STATA file.