Thrombosis prevention trial: follow-up study of practical implications.

The impact of randomised controlled trials on subsequent practice has only occasionally been assessed. Doing so is particularly necessary when unusual and possibly controversial treatments are being used. The aim of this study was to assess the practical implications of the results of the placebo-controlled primary prevention thrombosis prevention trial, in which the active treatment regimens were combined warfarin and aspirin, warfarin alone, and aspirin alone. Both active agents were given in low doses. Decisions on post-trial management were sought about men who continued with randomly-allocated treatment until the trial ended. The results of the trial appeared to have influenced decisions about future management. While aspirin was clearly the most frequent choice, a regimen involving warfarin was also used for a substantial proportion of men. Prior experience of acceptability, effectiveness, and safety probably played a significant part in decisions to continue with or switch to a warfarin-containing regimen. The findings may provide a measure of reassurance about the value of oral anticoagulation in other settings, particularly atrial fibrillation where, despite the results of trials showing major reductions in stroke, anticoagulation is underused.