External Control Arm

An external control arm refers to a comparison group in a clinical trial that is derived from data outside the study itself—such as previous clinical trials, real-world evidence, or patient registries—instead of being recruited and randomized alongside the investigational group. This approach is often used in rare or complex disease research where traditional control groups may be difficult or unethical to establish. External control arms support evidence generation by providing a relevant benchmark for evaluating treatment effectiveness while reducing patient burden and trial duration.

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