Thrombophilia screening tests

In general, thrombophilia screening tests are less useful than you might think for predicting risk of recurrence of the VTE (i.e. DVT or PE).  This is because whatever risk factor(s) caused the initial clot could equally well cause a repeat clot, unless you can identify a reversible risk factor (eg recent surgery), and this applies irrespective of whether or not you pick up these risk factors by lab testing.

If no reversible risk factor is identifiable (e.g. injury, surgery, oestrogens… ), check thoroughly for malignancy – up to 20% of clots are associated with malignancy.

Check for a persuasive family history of spontaneous deep venous thrombosis / PE.  This would increase the chances of a congenital cause for DVTs being identifiable and would make thrombophilia lab testing more productive (both for the patient and potentially for other family members).

Conversely, if there is a negative family history and if the patient has successfully come through significant surgery / pregnancy without developing a clot, the likelihood of a congenital thrombophilic tendency is a lot lower.

All that said, here is a panel of thrombophilia tests, to be used where appropriate:

· Lupus anticoagulant should preferably be done when the patient is not receiving warfarin, but if really necessary can be attempted while they are.

Tests that cannot be done while the patient is on warfarin (so better to do e.g. before starting warfarin):

· Protein C

· Protein S

· Anti-thrombin III

· Activated protein C resistance (the screening test for Factor V Leiden)

Tests that CAN be done while the patient is on warfarin:

· Prothrombin mutation G20210A (CPD tube – i.e. yellow top - as is a DNA test – NB expensive test)

· Factor V Leiden (but this is an expensive DNA test so do the screening test first, i.e. activated protein C resistance (APCR) – see above)

· ANA

· FVIII level

· D-D dimers

· B12/folate