Term
Single-arm study
A trial where every participant receives the study drug and there is no concurrent comparison group.
Single-arm studies report outcomes like 'sixty percent of patients responded' with no randomized group showing what would have happened without the drug. In diseases where the natural course fluctuates or where response criteria are soft, that number is uninterpretable on its own.
A ninety percent response rate in a single-arm study is exactly as uncontrolled as a ten percent one; this site's rubric grades the design, and the reported rate itself never moves a trial between grades.
On this site: The rubric's design criteria ↗
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