An uncontrolled clinical trial is characterized by which design feature?

• A. A randomized controlled trial.
• B. A before-and-after comparison without a separate untreated control group.
• C. A case-control study with matched controls.
• D. A cross-sectional survey.

Answer: (B)

An uncontrolled clinical trial is defined by the absence of a separate comparison group. The intervention’s effect is evaluated by comparing outcomes before and after within the same group, without a parallel untreated or alternative-treatment group to contrast against. This lack of a control makes it hard to separate the treatment effect from natural disease progression, regression to the mean, placebo effects, or other confounders, which is why this design is more prone to bias.

The other designs include randomized allocation with a control group, retrospective or prospective comparison with matched controls, and a single-time-point survey, none of which match the idea of a before-and-after comparison without an untreated control.