Blinding (sometimes called 'masking') refers to a set of techniques designed to reduce bias in clinical trials. A double-blind trial is where neither the patient nor the observer/clinician is aware of whether the patient is in the control or experimental arm of a trial. A single-blind trial is where the patient (or observer/clinician) is aware of which arm they are in but the observer/ clinician (or patient) is not. A triple-blind trial is one in which subjects, observers/clinicians and analysts are unaware of patient assignment to the arms of the trial. In trials of different styles of patient management or many surgical procedures, full blinding is often, alas, impossible. The seriousness of the potential bias will then depend on the circumstances. For example, blinding patients to the treatment they receive in a controlled trial matters less when the outcome measures are objectively observable events, like death, rather than subjective, like the relief of pain. However, even in surgery, patient blinding is possible. For example, in a trial of surgery for osteoarthritis of the knee the controls underwent a sham procedure, having a small slit cut in the side of the knee that was then sewn up again.
Was this article helpful?