Differences in treatment preferences between persons who enrol and do not enrol in a clinical trial

Ann R Coll Physicians Surg Can. 2001 Aug;34(5):292-6.


Objective: To quantitatively compare preferences for treatment between persons who enrolled in a randomized controlled trial (RCT) and those who were eligible but chose not to enrol.

Interventions: Participants' thresholds for treatment were determined using a probability trade-off technique. Pertinent health states were described. If not taking Aspirin, the probabilities of stroke, myocardial infarction (MI), and major bleeding were given. Given the risks and benefits of chronic Aspirin therapy, a systematic approach was used to determine patients' thresholds for treatment (the smallest reduction in stroke or MI risk of which patients were willing to take Aspirin).

Results: Of 54 participants, 42 enrolled in the RCT, and 12 did not. Compared with persons who enrolled, those who did not enrol required significantly greater increments in treatment benefit to be willing to take Aspirin.

Conclusions: This study shows differences in thresholds for treatment between persons who enrolled in a clinical trial and those who chose not to. Such attitudinal differences may lead to difficulty in the interpretation of clinical trials, especially those using health-related quality-of-life measures. More studies are needed to determine whether the attitudinal differences affect the generalization of results from clinical trials.

Publication types

  • Comparative Study

MeSH terms

  • Aspirin / therapeutic use
  • Attitude to Health*
  • Humans
  • Myocardial Infarction / prevention & control
  • Patient Participation*
  • Patient Selection*
  • Randomized Controlled Trials as Topic*
  • Research Design
  • Research Subjects / psychology*
  • Risk Assessment
  • Stroke / prevention & control
  • Therapeutic Human Experimentation*


  • Aspirin