English translation: controlled versus active comparator
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Explanation: In the absence of more context, this is how I'd translate it for an informed consent. The patient signing the consent is probably being asked to agree to participate in a clinical study that compares an inactive substance (i.e., placebo) with an active one (perhaps a new drug). The study is 'controlled' because it controls the active substance with one that is not active, thus elimintaing the "placebo effect" (i.e., psychological / physical feeling that the new drug is 'magic' and will cure the ailment).