Assessment of double-blindness at the conclusion of the beta-Blocker Heart Attack Trial
R. P. Byington, J. D. Curb and M. E. Mattson
At the conclusion of a double-blinded, randomized clinical trial of
propranolol hydrochloride, but before unblinding, the patients and clinic
personnel were asked to guess the treatment group assignment of each
patient. While 79.9% of the patients receiving propranolol correctly
identified their treatment group assignment, 57.2% of the patients
receiving placebo incorrectly guessed that they were also in the
propranolol group. No specific mechanism was identified to explain why more
patients receiving propranolol were better able to guess their group
assignment. Clinic physicians correctly identified the group assignment of
69.9% of the patients receiving propranolol and 68.8% of the patients
receiving placebo. Clinic coordinators correctly identified the group
assignment of 67.1% of the patients receiving propranolol and 70.6% of the
patients receiving placebo. For clinic personnel, heart rate level and
heart rate change seem to be the mechanisms employed to identify their
patients' treatment assignment.
