Research aimed to evaluate the relative effects of different health-care interventions, based on the idea that there must a fair comparison of the alternatives in order to know which is better. Threats to a fair comparison include the play of chance and bias, both of which can cause people to draw the wrong conclusions about how effective a treatment or procedure is.
An appreciation of the need to account for chance and bias has led to development of methods where new treatments are compared to either a PLACEBO or the standard treatment (or both) in a controlled, randomised clinical trial. ‘Controlled’ means that there is a comparison group of patients not receiving the test intervention, and ‘randomised’ implies that patients have been assigned to one or other treatment group entirely by chance and not because of their or their doctor's preference. If possible, trials are ‘double-blind’ – that is, neither the patient nor the investigator knows who is receiving which intervention until after the trial is over. All such trials must follow proper ethical standards, with the procedure fully explained to patients and their consent obtained.
The conduct, effectiveness and duplication of clinical trials have long been the subject of debate. Apart from occasional discoveries of deliberately fraudulent research (see RESEARCH FRAUD AND MISCONDUCT), the structure of some trials is unsatisfactory, statistical analyses are sometimes disputed and major problems have been the – usually unwitting – duplication of trials and non-publication of some trials, restricting access to their findings. Duplication may occur because no formal international mechanism exists to enable research workers to discover whether a clinical trial they are planning is already underway elsewhere, or has been completed but never published, perhaps because the results were negative, or no journal was willing to publish it, or the authors or funding authorities decided not to submit it for publication.
Given the widening recognition of the importance to patients and doctors of the practice of EVIDENCE-BASED MEDICINE, the easy availability of information on planned, ongoing and completed clinical trials is vital.