Background: Because of the growing value attributed to informed consent, competence assessment has become an important task for physicians and researchers, particularly when treatment and research involve persons who may be cognitively impaired, such as those with Alzheimer's dementia.
Methods: We developed and validated a 12-item questionnaire to assess the understanding of information about clinical trials by research subjects (score 0 to 24). The 12 questions were selected from a larger pool of 16 through internal consistency validity testing. We used the instrument in a pilot study involving 42 patients with mild to moderate Alzheimer's disease who had been asked to take part in two randomized clinical trials, and 21 caregivers.
Results: Patients with Alzheimer's disease had poor understanding (mean global score on questionnaire: 6.1+/-3.5). Unlike patients, caregivers understand the key elements of the clinical trials (questionnaire mean global score: 21.5+/-2.3; p for difference with patients <0.0001). In the group of patients, the score on the questionnaire correlated weakly with the Mini Mental State Exam (r=0.351; p=0.023), but more strongly with years of education in the group of caregivers (r=0.548; p=0.010) and age (r=-0.540; p=0.011).
Conclusions: Patients with Alzheimer's disease of mild to moderate severity show poor understanding of the design, risks and benefits of clinical trials. Enrolment of these patients in clinical trials must be accompanied by adequate measures for patient protection.