What is a Double Blind Trial?

A double-blind study: What is a Double-Blind Trial?

Clinical trials are scientific experimental studies that assess the efficacy and safety of new potential treatments for certain disorders and conditions.

The time taken for research and development before the clinical trial phase can vary widely depending on the drug and disease being studied.

After the different phases of clinical trials are completed, the results can be used to decide whether the drug or treatment should be made available to the public or rejected by the Food and Drug Administration (FDA).

There are usually three parties or groups involved in the study: the patients or the study participants, the doctors or researchers, the monitoring committee or any other third party.

Depending on how many parties are unaware of the details of the interventional and placebo groups, single-blind, double-blind, or triple-blind studies can be performed.

The most trusted and secure clinical trial method is a double-blind trial, as it prevents several forms of bias and ensures the accuracy of the study’s results.

What is a double-blind trial?

A double-blind study is an experimental study where the researcher and the participants are unaware of the specifics of the treatment plans and allocations.

In simple terms, neither the participants nor the researchers know which patient is receiving the new treatment and which one is receiving an old treatment option or a placebo drug.

CONSORT guidelines emphasize clear reporting rather than changing the definition of double-blind; they recommend describing who is blinded among the participants, caregivers, and those assessing outcomes.

This is because this term doesn’t explain strictly which party was blinded and the specifics of the blinding.

Hence, researchers must specify details rather than use the term double-blind when referring to a study where the researchers and participants were blinded.

How is a double-blind study performed?

For a double-blind trial, participants are divided into the interventional and placebo groups.

The participants in the interventional group are given the treatment or drug whose effects are being studied.

Participants in the placebo group received a placebo or standard treatment, not different treatments, based on the study’s primary aim, which is to maintain consistency and control within the study.

If the study aims to assess whether a new treatment is better than the current treatment, the placebo group will receive the current treatment; if the study aims to find new treatments for a condition, a placebo drug will be given.

It is the responsibility of a third party or an independent group, not the monitoring committee specifically, to allocate participants to groups in a blinded manner.

All medications are typically packaged to appear identical to ensure blinding, not necessarily sealed in bags.

Advantages of Double-blind trial

A double-blind study has many benefits, the most important of which is a significant reduction of bias.

Bias usually refers to any interpretation of the information that departs from the results. Several forms of bias can occur in a clinical study, and a double-blind trial can help avoid them.

To prevent treatment assignment bias, participant allocation in a double-blind study is random and not influenced by doctors.

This is a form of bias as the results will be skewed and favor the interventional group, although the reality may differ.

Similarly, if a patient is made aware that they are receiving the placebo treatment, they may worsen medically as they don’t believe in the treatment.

Their belief system can ruin their chances; again, it has nothing to do with the efficacy or safety of the drug being tested.

At the same time, if they are receiving the new treatment and are aware of this, they may believe in its efficacy regardless of the actual results, which could skew the data.

This is yet another form of bias that should be avoided if the actual results of the study are to be studied.

Unblinding of a double-blind trial

During a double-blind trial, it is possible for unblinding to occur.

Unblinding, as the name aptly describes, occurs when either of the blinded groups discovers information they weren’t supposed to know.

For example, if a patient finds out which study group they are in during the study period, this is called unblinding.

If unblinding occurs, it must be reported in the study results, but it is treated as a potential source of contamination.

Hence, great care should be taken when performing a double-blind study.

See Also

Laser Eye Surgery Clinical Trials

How Much Do Clinical Trials Pay

What is a Randomized Clinical Trial

Current Version
July 26, 2021
Written By
Daniyal Haider, MD
April 16, 2024
Updated By
Daniyal Haider, MD

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