Adjudication committee: An Adjudication Committee of three thromboembolism experts not otherwise involved in this study will be convened.All reported hemorrhagic and thrombotic events will be reviewed by this committee, which will use all available source documentation to adjudicate clinical events. This committee will be convened when complete data are available on the first 20 bleeds or clots, and subsequently with each multiple of 20 events. To ensure uniformity, all episodes of hemorrhage will be adjudicated according to pre-specified criteria. The committee will report the results of their adjudication to the Coordinating Centre for inclusion in the study database. Although adjudication of all events may seem excessive it is possible that adjudication could "upgrade" events deemed minor by the site investigator, highlighting the need for central review of all bleeding events.