Laboratory Test Reference Guide

Testing for Factor V Leiden and Prothrombin Mutation are an essential component of this screening. Please ensure these are ordered.

1 x 1.5 mL double spun platelet poor plasma. 1.4 mL EDTA whole blood.

Send platelet poor plasma frozen, EDTA ambient.

The following recommendations are for inherited thrombophilia. There are other indications for testing for acquired thrombophilic factors such as antiphospholipid antibodies. Seek consultant advice.

• Do not conduct thrombophilia testing in adult patients under the age of 50 years unless the first episode of venous thromboembolism (VTE) occurs:

-   in the absence of a major transient risk factors (surgery, trauma, immobility), or

-   in the absence of oestrogen-provocation, or

-   at an unusual site.

• Do not request an inherited thrombophilia evaluation for women with histories of pregnancy loss, intrauterine growth restriction (IUGR), preeclampsia and abruption. (Specific testing for antiphospholipid antibodies, when clinically indicated, should be limited to lupus anticoagulant, anticardiolipin antibodies and beta 2 glycoprotein antibodies).

The DHB Shared service guidelines include:

Only test in:

• Idiopathic (unprovoked) VTE in young patients (<45 years)
• Warfarin-induced skin necrosis 
• Children presenting with purpura 
• Siblings of patients with homozygous FVL, homozygous PT20210A  or compound heterozygotes
• Thrombosis in unusual sites (e.g. cerebral, mesenteric, portal) * but see next page
• Testing for other reasons should only be performed after consultation with a Haematologist.

*Note: the latest UK and US guidelines (NICE, BCSH, ACCP) now restrict thrombophilia testing in young patients with idiopathic VTE to those who also have a first degree family history of unprovoked VTE and    no longer recommend testing for thrombosis in unusual sites.

Testing is also not indicated in patients who already have an indication for extended therapy in VTE.

Testing may also be useful in women with a VTE not provoked by hormonal therapy and who may get pregnant. Always discuss testing in such patients with a Haematologist.

Consider referral of patients with the following to Haematology for advice or follow up:

• Unprovoked VTE in those <50 years of age
• All pregnant patients or patients with previous VTE planning pregnancy
• Recurrent VTE if compliant with treatment and despite a therapeutic INR
• Recurrent VTE if not being treated and not previously investigated by Haematology
• Identified high risk thrombophilia (protein S/C and antithrombin III deficiency or compound heterozygotes of prothrombin/FVL mutations)
• Active malignancy
• Uncertainty about the duration of anticoagulation

The genetic thrombophilia tests will only be performed once in a patient’ life time.

It is recommended that testing for the presence of the lupus anticoagulant also be included in the laboratory evaluation of thrombophilic patients. This should also include anticardiolipin antibodies (Immunology). For requests referred from other laboratories, lupus anticoagulant will only be included if specifically asked for.

1ml double spun platelet poor plasma