You are about to leave an AbbVie Canada site, a Web site maintained by AbbVie Corporation.

This link is provided for your convenience only. AbbVie Corporation takes no responsibility for the content of any Web site maintained by any third party and makes no representation as to the accuracy or completeness of any information contained on this or any subsequent link.

Do you wish to leave this site?

Yes No

You are here

About blinded studies

What is blinding?

Blinding — or masking — is the process by which one or more parties involved with the trial do not know which patients have been assigned to which treatments. Types of blinding are explained below: single-blind, double-blind, triple-blind and no blinding (called open-label).

Why is blinding used?

The purpose of blinding is to prevent biases: if researchers knew which patient was getting the study treatment and which was getting the placebo, they might be tempted to give the (presumably helpful) study drug to a patient who could more easily benefit from it. A researcher might also give extra care to only the patients taking placebos to compensate for their ineffectiveness.

Not knowing which participants are receiving the active treatment allows the trial doctor and research staff to objectively observe patients during the study. Regardless of which treatment the patients get, however, the level of medical attention and care they receive is the same.

Similarly, a patient who does not know which treatment they are receiving cannot form an opinion about it that could unfairly influence the trial results.

What types of blinding can be used in trials?

Single-blind: The researchers are aware of the treatment they are administrating but patients don’t know which treatment they are receiving.

Double-blind: Two of the parties involved with the trial do not know which patients have been assigned to which treatments. Typically, this includes the researchers and the patients.

Triple-blind: Three of the parties involved do not know which patients have been assigned to which treatments. This often includes the researchers conducting the study, the patients, and the researchers analyzing the results collected.

Open-label: A trial in which blinding is not used. All parties involved know which patients have been assigned to which treatments.