Venous Thromboembolism: Risk factors

Which one of the following statements regarding the etiology of venous thromboembolism (VTE) is correct?
A. Third generation combined oral contraceptive pills are safer than second generation ones
B. VTE develops in around 5% of patients with rheumatoid arthritis
C. Female gender is a risk factor recurrent VTE
D. The second trimester of pregnancy is associated with a greater risk than the puerperium
E. Tamoxifen therapy increases the risk of VTE

Answer:
E. Tamoxifen therapy increases the risk of VTE

Discussion:
Venous thromboembolism: Risk factors 
Common predisposing factors include malignancy, pregnancy and the period following an operation. The comprehensive list below is partly based on the 2010 SIGN venous thromboembolism (VTE) guidelines:
General 
 increased risk with advancing age
 obesity
 family history of VTE
 pregnancy (especially puerperium)
 immobility
 hospitalisation
 anaesthesia
 central venous catheter: femoral >> subclavian

Underlying conditions
 malignancy
 thrombophilia: e.g. Activated protein C resistance, protein C and S deficiency
 heart failure
 antiphospholipid syndrome
 Behcet's syndrome
 polycythaemia
 nephrotic syndrome
 sickle cell disease
 paroxysmal nocturnal haemoglobinuria
 hyperviscosity syndrome
 homocystinuria

Medication
 combined oral contraceptive pill: 3rd generation more than 2nd generation
 hormone replacement therapy: the risk of VTE is higher in women taking oestrogen + progestogen preparations compared to those taking oestrogen only preparations
 raloxifene and tamoxifen
 antipsychotics (especially olanzapine) have recently been shown to be a risk factor

It should be remembered however that around 40% of patients diagnosed with a PE have no major risk factors.