The risk of bleeding with different anticoagulants is not addressed in this table. The increase in bleeding associated with a risk factor will vary with: (1) severity of the risk factor (eg, location and extent of metastatic disease; platelet count); (2) temporal relationships (eg, interval from surgery or a previous bleeding episode197 ); and (3) how effectively a previous cause of bleeding was corrected (eg, upper GI bleeding). c Important for parenteral anticoagulation (eg, rst 10 d), but less important for long-term or extended anticoagulation. d Although there is evidence that risk of bleeding increases with the prevalence of risk factors,187,188,192,194,195,196,198,201,202,204,217,218 the categorization scheme suggested here has not been validated. Further- more, a single risk factor, when severe, will result in a high risk of bleeding (eg, major surgery within the past 2 d; severe thrombocytopenia). e Compared with low-risk patients, moderate-risk patients are assumed to have a twofold risk and high-risk patients are assumed to have an eightfold risk of major bleeding.79,185,187,189,195,196,198,204 f We estimate that anticoagulation is associated with a 2.6-fold increase in major bleeding based on comparison of extended anticoagulation with no extended anticoagulation (Table 6 in AT91 ). 