Page 384 - Essential Haematology

370 / Chapter 27 Thrombosis and antithrombotic therapy

and livedo reticularis is a frequent dermal 5 Thrombin time (and reptilase time) – prolonga-
manifestation. tion suggests an abnormal fi brinogen.
Treatment is with anticoagulation where indi- 6 Fibrinogen assay.
cated. It is usual to maintain an international nor- 7 APC resistance test and DNA analysis for factor
malized ratio (INR) of between 2.0 and 3.0 with V Leiden.
warfarin but higher levels may be needed if previous 8 Antithrombin – immunological and functional
arterial or major DVT has occurred or recurrence assays.
of thrombosis occurs on warfarin therapy. Low dose 9 Protein C and protein S – immunological and
heparin and aspirin are useful in the management functional assays.

of recurrent miscarriage. 10 Prothrombin gene analysis for the G20210A
Collagen vascular diseases and Beh ç et ’ s syn- variant.
drome are also associated with arterial and venous 11 Plasma homocysteine estimation.

thrombosis, whether or not the lupus anticoagulant 12 Test for CD59 and CD55 expression (paroxys-
is present (see p. 369 ). mal nocturnal haemoglobinuria) in red cells
if paroxysmal nocturnal haemoglobinuria is
suspected.
Investigation of t hrombophilia
13 Test for JAK2 (V617F) mutation if portal or
Many of the conditions associated with an increased hepatic vein thrombosis.
thrombotic risk are obvious following clinical exam- 14 Protein electrophoresis for paraprotein.
ination. A full assessment is indicated, particularly
in patients who have recurrent or spontaneous Diagnosis of v enous t hrombosis
DVT or PE, in patients who have thrombosis at a
young age and in those patients with a familial
Deep v ein t hrombosis
tendency to thrombosis or thrombosis at an unusual
site. It is also needed in women with recurrent fetal Clinical suspicion DVT is suspected in those

loss. With the increasing recognition of systemic with previous DVT, cancer or confined to bed. In
causes of thrombophilia, the indications for throm- the leg, unilateral thigh or calf swelling or tender-
bophilia screening are widening. Th e following ness, pitting oedema and the presence of collateral
laboratory tests are used in diagnosis. superficial non - varicose veins are important signs.

’
Homan s sign (pain in the calf on fl exing the ankle)
is usually positive.
Screening t ests

Serial compression ultrasound This is a reli-
1 Blood count and erythrocyte sedimentation able and practical method for patients with fi rst
rate – to detect elevation in haematocrit, suspicion of DVT in the legs and other sites (Fig.
white cell count, platelet count, fi brinogen and 27.2 a). It can be combined with spectral, colour
globulins. (Fig. 27.2 ) or power Doppler (duplex) scanning
2 Blood film examination – may provide evidence which improves accuracy by focusing on individual

of myeloproliferative disorder; leucoerythrob- veins. It does not distinguish between acute and
lastic features may indicate malignant chronic thrombi. Persisting venous obstruction
disease. detected by ultrasonography at the completion of
3 Prothrombin time (PT) and APTT – a short- warfarin therapy is associated with an increased risk

ened APPT is often seen in thrombotic states of recurrent thrombosis.
and may indicate the presence of activated clot- Contrast venography This most sensitive pro-

ting factors. A prolonged APTT test, not cor- cedure is reserved for patients with highly suggestive

rected by the addition of normal plasma, clinical findings but negative ultrasonography.
suggests an LA or an acquired inhibitor to a Iodinated contrast medium is injected into a vein
coagulation factor. peripheral to the suspected DVT. Th is permits
4 Anticardiolipin and anti - β 2 - GPI antibodies. direct demonstration by X - ray of the site, size and