How is blinding defined in a clinical trial?

How is blinding defined in a clinical trial?

• A. Keeping participants and/or researchers unaware of the assigned treatment to reduce bias
• B. Keeping participants aware of their treatment
• C. Allowing investigators to know the treatment
• D. Unblinding all participants at the start

Answer: (A)

Blinding means keeping key people involved in a trial—participants and sometimes researchers or assessors—unaware of which treatment a participant has been assigned, in order to prevent bias from expectations or beliefs. When participants don’t know what they’re receiving, their reporting of symptoms or perceived effects isn’t colored by hopes or placebo effects. When those assessing outcomes don’t know the treatment, their judgments aren’t swayed by prior beliefs about effectiveness. This is why this choice—keeping participants and/or researchers unaware of the assigned treatment to reduce bias—is the best description. If participants know what they’re receiving, or investigators know the assignment, bias can creep in—participants might over- or under-report outcomes, and investigators might unconsciously interpret results in line with expectations. Unblinding at the start would fully negate the protective effect of blinding, and having investigators know the assignment similarly undermines the objectivity of outcome assessment.

Blinding means keeping key people involved in a trial—participants and sometimes researchers or assessors—unaware of which treatment a participant has been assigned, in order to prevent bias from expectations or beliefs. When participants don’t know what they’re receiving, their reporting of symptoms or perceived effects isn’t colored by hopes or placebo effects. When those assessing outcomes don’t know the treatment, their judgments aren’t swayed by prior beliefs about effectiveness. This is why this choice—keeping participants and/or researchers unaware of the assigned treatment to reduce bias—is the best description.

If participants know what they’re receiving, or investigators know the assignment, bias can creep in—participants might over- or under-report outcomes, and investigators might unconsciously interpret results in line with expectations. Unblinding at the start would fully negate the protective effect of blinding, and having investigators know the assignment similarly undermines the objectivity of outcome assessment.