Exposure analysis of dichotomous response measures in long-term studies.

Differential exposure to study medications in long-term studies of some cardiovascular compounds complicates analyses, particularly the usual intention-to-treat analyses and inferences therefrom of the data collected. Analysis methods that incorporate exposure are developed, presented, and illustrated by applying them to primary response data from a long-term, placebo-controlled, ancillary trial of gemfibrozil. The analysis methods address the extent to which end-points are correlated with the actual use of the compound rather than the extent to which end-points are correlated with the random assignment to double-blind study medications.