Risk factors and venous thromboembolism
| Transient risk factors (risk factors that resolve after they have provoked VTE)* |
| Major transient risk factors (occur within 3 mo of VTE diagnosis); examples include: |
| Surgery with general anesthesia for ≥30 min |
| Confined to bed in hospital for ≥3 d with an acute illness (“bathroom privileges” only) |
| Cesarean section |
| Minor transient risk factors (occur within 2 mo of VTE diagnosis); examples include: |
| Surgery with general anesthesia for <30 min |
| Admission to hospital for <3 d with an acute illness |
| Estrogen therapy (eg, oral contraceptives, hormone replacement therapy) |
| Pregnancy and puerperium |
| Confined to bed out of hospital for ≥3 d with an acute illness |
| Leg injury associated with decreased mobility for ≥3 d |
| Chronic (persistent) risk factors (risk factors that persist after the development of VTE)† |
| Active cancer (eg, ongoing chemotherapy; recurrent or progressive disease) |
| Inflammatory bowel disease |
| Autoimmune disorders (eg, antiphospholipid syndrome, rheumatoid arthritis) |
| Chronic infections |
| Chronic immobility (eg, spinal cord injury) |
| Transient risk factors (risk factors that resolve after they have provoked VTE)* |
| Major transient risk factors (occur within 3 mo of VTE diagnosis); examples include: |
| Surgery with general anesthesia for ≥30 min |
| Confined to bed in hospital for ≥3 d with an acute illness (“bathroom privileges” only) |
| Cesarean section |
| Minor transient risk factors (occur within 2 mo of VTE diagnosis); examples include: |
| Surgery with general anesthesia for <30 min |
| Admission to hospital for <3 d with an acute illness |
| Estrogen therapy (eg, oral contraceptives, hormone replacement therapy) |
| Pregnancy and puerperium |
| Confined to bed out of hospital for ≥3 d with an acute illness |
| Leg injury associated with decreased mobility for ≥3 d |
| Chronic (persistent) risk factors (risk factors that persist after the development of VTE)† |
| Active cancer (eg, ongoing chemotherapy; recurrent or progressive disease) |
| Inflammatory bowel disease |
| Autoimmune disorders (eg, antiphospholipid syndrome, rheumatoid arthritis) |
| Chronic infections |
| Chronic immobility (eg, spinal cord injury) |
Patients may present with >1 transient risk factor or a combination of transient and chronic risk factors. Nonenvironmental risk factors for VTE include hereditary thrombophilia, older age, and male sex. These variables typically exhibit a low relative risk for VTE but may be useful in combination with acquired risk factors when considering an individual patient's risk for recurrence. Other acquired variables that confer a very weak risk for recurrence (OR < 2), such as obesity, varicose veins, or laparoscopic surgery, are not considered significant risk factors individually, but they may have an additive effect when combined with other risk factors listed above. Adapted from Kearon et al237 and Konstantinides et al238 with permission.
For patients with VTE and a major transient risk factor >3 months prior to the VTE or a single minor transient risk factor >2 months prior to the VTE, clinical judgment is essential when considering the contribution of this variable to the initial VTE and the risk of recurrence.
Chronic risk factors may fluctuate over time (eg, curative treatment of cancer or clinical waxing and waning of an autoimmune disorder), which may impact the relative risk of recurrent VTE. Active cancer is addressed in a future guideline document from ASH and is not considered in this article.