A clinical trial is an experiment involving persons done to assess the safety and efficacy of a treatment. The modifier “clinical” draws attention to the fact that the experiment is being carried out in a clinical setting focused on clinical disease. Generally the modifier is dropped when context is clear.
“Clinical trial” is a publication type in the National Library of Medicine indexing system; defined as:
Pre-planned clinical study of the safety, efficacy, or optimum dosage schedule of one or more diagnostic, therapeutic, or prophylactic drugs, devices, or techniques in humans selected according to predetermined criteria of eligibility and observed for predefined evidence of favorable and unfavorable effects.
Trials having comparison treatments are referred to as “controlled” – a trial involving one or more test treatments, at least one control treatment, and concurrent enrollment, treatment, and followup of study subjects.
A randomized controlled trial in PubMed is a:
Trial that involves at least one test treatment and one control treatment, concurrent enrollment and follow-up of the test-and control-treated groups, and in which the treatments to be administered are selected by a random process, such as the use of a random-numbers table. (http://www.ncbi.nlm.nih.gov/sites/mesh)
A multicenter trial involves two or more administratively distinct study centers, a common treatment protocol, and a leadership ...