Use of dose modification schedules is effective for blinding trials of warfarin: evidence from the WASID study.

Background: Randomized clinical trials are blinded to prevent knowledge of treatment assignment from influencing outcomes and their assessments, thus protecting the trial's scientific integrity. Trials involving a warfarin treatment arm are difficult to blind due to the need to continuously adjust dose.

Purpose: We sought to examine the effectiveness of blinding secondary stroke prevention trials with a warfarin treatment arm in which the blinding system incorporates use of placebo warfarin dose modification schedules for patients in the placebo warfarin arm.