Risk factors for bleeding with anticoagulant therapy and estimated risk of major bleeding in low, moderate, and high risk categories

Risk factors*
Age >65 years Age >75 years Previous bleeding Cancer Metastatic cancer Renal failure Liver failure Thrombocytopenia Previous stroke Diabetes Anemia Antiplatelet therapy Poor anticoagulant control Comorbidity and reduced functional capacity Recent surgery^¶ Frequent falls Alcohol abuse
Estimated absolute risk of major bleeding (%)
Categorization of risk of bleeding^Δ	Low risk^◊ (0 risk factors)	Moderate risk^◊ (1 risk factor)	High risk^◊ (≥2 risk factors)
Anticoagulation 0 to 3 months^§
Baseline risk (%)	0.6	1.2	4.8
Increased risk (%)	1	2	8
Total risk (%)	1.6^§	3.2	12.8^¥
Anticoagulation after first 3 months^‡
Baseline risk (%/years)	0.3^†	0.6	≥2.5
Increased risk (%/years)	0.5	1	≥4
Total risk (%/years)	0.8**	1.6**	≥6.5

GI: gastrointestinal; UFH: unfractionated heparin; LMWH: low molecular weight heparin; VKA: vitamin K-dependent antagonist (ie, warfarin); VTE: venous thromboembolism.

* 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 episode), and (3) how effectively a previous cause of bleeding was corrected (eg, upper-GI bleeding).

¶ Important for parenteral anticoagulation (eg, first 10 days), but less important for long-term or extended anticoagulation.

Δ Although there is evidence that risk of bleeding increases with the prevalence of risk factors, this categorization scheme has not been validated. Furthermore, a single risk factor, when severe, will result in a high risk of bleeding (eg, major surgery within the past 2 days, severe thrombocytopenia).

◊ Compared with low-risk patients, moderate-risk patients are assumed to have a 2-fold risk and high-risk patients an 8-fold risk of major bleeding.

§ The 1.6% corresponds to the average of major bleeding with initial UFH or LMWH therapy followed by VKA therapy. We estimated baseline risk by assuming a 2.6 relative risk of major bleeding with anticoagulation (refer to footnote ‡).

¥ Consistent with frequency of major bleeding observed by Hull et al in high-risk patients^[1].

‡ 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. The relative risk of major bleeding during the first 3 months of therapy may be greater than during extended VKA therapy because (1) the intensity of anticoagulation with initial parenteral therapy may be greater than with VKA therapy; (2) anticoagulant control will be less stable during the first 3 months; and (3) predispositions to anticoagulant-induced bleeding may be uncovered during the first 3 months of therapy. However, studies of patients with acute coronary syndromes do not suggest a ≥2.6 relative risk of major bleeding with parenteral anticoagulation (eg, UFH or LMWH) compared with control.

† Our estimated baseline risk of major bleeding for low-risk patients (and adjusted up for moderate- and high-risk groups as per footnote ◊).

** Consistent with frequency of major bleeding during prospective studies of extended anticoagulation for VTE.

Reference:

Hull RD, Raskob GE, Rosenbloom D, et al. Heparin for 5 days as compared with 10 days in the initial treatment of proximal venous thrombosis. N Engl J Med 1990; 322:1260.

Reproduced from: Kearon C, Akl EA, Comerota AJ, et al. Antithrombotic therapy for VTE disease: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest 2012; 141:e419S. Table used with the permission of Elsevier Inc. All rights reserved.

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Risk factors for bleeding with anticoagulant therapy and estimated risk of major bleeding in low, moderate, and high risk categories