How blind was the patient blind in AMIS?

Area of Science:

• Cardiology
• Clinical Trial Methodology
• Pharmacology

Background:

• The Aspirin Myocardial Infarction Study (AMIS) investigated aspirin's effect on survival post-heart attack.
• Maintaining patient blinding is crucial for the validity of double-blind, placebo-controlled trials.

Purpose of the Study:

• To assess patient awareness of their treatment assignment in the AMIS trial.
• To evaluate the integrity of the patient blind based on perceived treatment allocation.

Main Methods:

• A subset of 380 participants from the AMIS trial were interviewed about their perceived treatment.
• Analysis included correct identification, mistaken assignment, and uninformed guesses regarding therapy.

Main Results:

• Only 52% of interviewed participants correctly identified their assigned therapy (aspirin or placebo).
• A significant portion (28%) mistakenly identified the alternative treatment, and 24% made "informed" guesses.
• Testing capsules (e.g., by taste) correlated with more accurate responses, as did reasons for guessing, such as side effects.

Conclusions:

• The patient blind in the AMIS trial was only partially maintained.
• Patient perceptions of treatment assignment were influenced by factors like capsule testing and experienced side effects.
• A majority of participants lacked certainty about their treatment allocation, impacting the interpretation of the blind's effectiveness.