open-label trial

An open-label trial is a study in which both the health providers and the patients are aware of the drug or treatment being given. It is also called a nonblinded study. The alternative is a blinded trial, in which the assignment is concealed from the patients, from the people treating and assessing them, or from both.

Trials are run open label for practical reasons. Two regimens can differ in how they are given, how often and for how long, so concealing which one a patient is receiving may be impossible without procedures that would themselves be a burden on people who are already ill. The trade-off is that knowledge can influence judgement. When patients and their doctors know the assignment, it can affect how symptoms are reported and how far a judgement call goes one way or the other. Open-label results therefore carry most weight when the main measure is a hard one, such as death, or a scan assessed by reviewers who were kept unaware of which treatment the patient received.