Bleeding Events
Bleeding is the most frequent complication of warfarin therapy (5). A large body of evidence evaluating the safety
of warfarin therapy is available. In clinical trials, bleeding events are classified as fatal, major, life-threatening,
clinically significant, overt, or minor. ‘Major bleeding’ is the most common safety outcome cited in clinical trials
but the definition varies across trials. According to the International Society on Thrombosis and Hemostasis, the
definition of major bleeding should be based on objective criteria and only include events which are life-threatening,
utilize major health-care resources, or result in death (5). A list of ICD-9 codes (Table 2) for bleeding events based
on the above criteria have been identified and used in a number of clinical trials and analyses evaluating warfarin
safety (5-8). We used this list to identify bleeding events in our patient population (Table 3).