Evidence-based medicine and randomized double-blind clinical trials: a study of flawed implementation

Area of Science:

• Clinical Trials
• Evidence-Based Medicine
• Psychology in Research

Background:

• Randomized double-blind clinical trials (RDBCTs) are fundamental to evidence-based medicine.
• Anomalous results in RDBCTs suggest the presence of unknown biases.
• Potential flaws in RDBCT implementation may explain these biases.

Purpose of the Study:

• To identify a potential flaw in RDBCT implementation causing biases.
• To investigate how experimenter expectations can compromise blinding.
• To emphasize the need for monitoring blinding maintenance in RDBCTs.

Main Methods:

• Analysis of RDBCT implementation flaws.
• Discussion of social psychological factors influencing experimenter bias.
• Review of existing RDBCT design features and their limitations.

Main Results:

• A key flaw is the breaking of the double-blind through experimenter beliefs and expectations.
• These expectations can lead to unconscious biases in patient assessment and cues.
• The observed treatment effect may be confounded by experimenter expectations rather than the treatment itself.

Conclusions:

• RDBCTs without monitored blinding maintenance risk compromised conclusions.
• Researchers must provide data demonstrating blinding maintenance, not just design assertions.
• Future RDBCTs should routinely include methods to monitor and account for experimenter beliefs and expectations to avoid confounding.