A Systematic Review focuses on a specific clinical question and uses an extensive literature search to identify studies with sound methodology. Studies are reviewed, assessed, and summarized according to the predetermined criteria of the review question.
A Meta-analysis combines the results of the systematic review with statistical methodology.
Randomized, controlled clinical trial - This is a prospective, analytical, experimental study using primary data generated in the clinical environment. Subjects are randomly allocated to two or more groups (treatment and control). The outcomes of the groups are compared at the conclusion of the study.
A study that shows the efficacy of a diagnostic test is called a prospective, blind comparison to a gold standard study. This is a controlled trial that studies patients with varying degrees of an illness and administers both diagnostic tests--the test under investigation and the "gold standard" test.