Matching quality of agents employed in "double-blind" controlled clinical trials.

In an inquiry into the matching quality of preparations employed in double-blind controlled clinical trials, a panel of 4 observers studied 22 pairs of agents used in a sample of such trials, examining features which might make one preparation distinguishable from the other. 5 pairs of substances were an excellent match, being virtually indistinguishable, but in 7 pairs ther were obvious differences, detected by all 4 observers. The preparations used in cross-over studies were not specially well matched. Colour differences were most readily detected, followed by taste. The observers differed in their ability to detect differences between pairs of preparations, and 1 panel member was approximately 3 times more successful in doing so than another.