Assessment of blindness in the Danish Verapamil Infarction Trial II (DAVIT II). Danish Study Group on Verapamil in Myocardial Infarction.

In a double-blind, randomized, placebo-controlled study comparing verapamil and placebo in late secondary intervention after acute myocardial infarction, the physicians were asked to try to identify the treatment in 100 consecutive patients. The assessment of the presumed treatment was based upon the presence of effects and side effects. It was only possible correctly to group 36% (95%: 26.7-46.2) of the patients. 35 patients were grouped as indeterminable. In 65 a treatment was proposed, correctly in 55%, and thus ideal blindedness had been achieved.