There has been much less research on participation in trials studying preventive measures (preventive trials).
Such attrition is not unusual in trials studying non-specific low back pain: Geisser et al, [ 15] lost 28% of subjects during their trial period, and Frost et al, [ 10] lost 30%, although most were lost to follow up.
A limitation of the present study is that the assessments will be performed by research assistants who cannot remain blinded to the treatment condition of the included patients, as is always the case in trials studying the effects of psychotherapy.
Stimulated C-peptide is currently accepted as the reference outcome for assessing beta-cell secretory response in trials studying the prevention of beta-cell loss in established autoimmune diabetes [ 9].
Furthermore, we found that cross-over design was not common in trials studying non-pharmacological treatments because the washout periods of these interventions could not be evaluated accurately, which may bring bias to outcome assessments.
Schultz et al [ 3] demonstrated that lack of randomisation is the major source of bias in trials; studies which are not randomised can lead to overestimation of treatment effects by up to 40%.
Despite this, Black women (as well as other minorities and women in general) have traditionally been vastly underrepresented in clinical trials studying the safety and efficacy of cardiovascular disease drugs.
A17 World Briefing A6 SCIENCE/HEALTH Minorities and H.I.V. Blacks and other members of ethnic minorities, who make up a growing percentage of Americans infected with the AIDS virus, are greatly underrepresented in clinical trials studying new treatments.
In each trial, study sites recruited participants through a combination of strategies described in more detail below.
In a trial study of people who wore the device for a few weeks, some users said their friends mistook the hearing aids for wireless headsets used with cellphones, Mr. Zaltman said.
