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Allocation Concealment


Randomization is concealed if the person who is making the decision about enrolling a patient is unaware of whether the next patient enrolled will be entered in the intervention or control group (using techniques such as central randomization, or sequentially numbered opaque sealed envelopes). If randomization is not concealed, patients with differing prognosis may be differentially recruited to treatment or control groups. Of particular concern, patients with better prognoses may tend to be preferentially enrolled in the active treatment arm resulting in exaggeration of the apparent benefit of the intervention (or even falsely concluding that the intervention is efficacious).

Categories: Bias Prevention