Predisposing factors for venous thromboembolism (data modified from Rogers et al. [23] and Anderson and Spencer [24])

Strong risk factors (OR >10)
 Fracture of lower limb
 Hospitalization for heart failure or atrial fibrillation/flutter (within previous 3 months)
 Hip or knee replacement
 Major trauma
 Myocardial infarction (within previous 3 months)
 Previous VTE
 Spinal cord injury
Moderate risk factors (OR 2–9)
 Arthroscopic knee surgery
 Autoimmune diseases
 Blood transfusion
 Central venous lines
 Intravenous catheters and leads
 Congestive heart failure or respiratory failure
 Erythropoiesis-stimulating agents
 Hormone replacement therapy (depends on formulation)
In vitro fertilization
 Oral contraceptive therapy
 Post-partum period
 Infection (specifically pneumonia, urinary tract infection, and HIV)
 Inflammatory bowel disease
 Cancer (highest risk in metastatic disease)
 Paralytic stroke
 Superficial vein thrombosis
Weak risk factors (OR <2)
 Bed rest >3 days
 Diabetes mellitus
 Arterial hypertension
 Immobility due to sitting (e.g. prolonged car or air travel)
 Increasing age
 Laparoscopic surgery (e.g. cholecystectomy)
 Varicose veins

HIV: human immunodeficiency virus; OR: odds ratio; VTE: venous thromboembolism.