Key Information

Appropriate Tests


Term used to indicate an increased inherited or acquired risk of thrombosis. See blood abnormalities under Thrombosis, arterial and venous.

Specific factor assays.

Factor V Leiden mutation

Factor V Leiden

Prothrombin gene mutation (G20210A)

Prothrombin gene mutation

Protein C, Protein S deficiency

Protein C, Protein S

Antithrombin deficiency


Activated Protein C resistance

APC resistance

Elevated F VIII:C


ABO blood group


Acquired causes


Underlying malignancy

May be occult. Particularly adenocarcinomas

Pregnancy and exogenous oestrogens such as OC or HRT


Immobility, postoperative state, venous stasis


Cardiolipin antibodies

Cardiolipin Ab. May be part of the Antiphospholipid syndrome.

Elevated homocysteine

This may be due to an underlying genetic lesion or reflect deficiency in Folate, Vitamin B12 and/or Pyridoxine in the diet. Testing for the methyl tetra hydrofolate reductase mutation may be indicated.

Lupus inhibitor


Myeloproliferative neoplasms


Paroxysmal nocturnal haemoglobinuria (PNH)

See Paroxysmal nocturnal haemoglobinuria; Myelodysplastic syndromes

Behcet’s disease


Chronic haemolysis, eg, thalassaemic states


Sickle cell anaemia

See Sickle cell disorders



Vascular/skeletal anomalies


Drugs, eg, heparins


Strong family history


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