Tests & Clinical Applications, Antiphospholipid syndrome, What treatment is available?

Treatment involves first-line use of low molecular-weight heparin (LMWH) or, where this agent is contraindicated, of unfractionated heparin (UFH), at a curative dose, with follow-on therapy, except if contraindicated, consisting of a vitamin K antagonist (VKA).
In certain cases, but not pregnant women, in whom it is contraindicated, Fondaparinux may be used to treat deep venous thrombosis or pulmonary embolism.
VKAs cause malformation syndrome in 4 to 7% of pregnancies between the 3rd and 9th weeks of gestation. VKAs should only be given where LMWH cannot be prescribed. If a VKA is used during pregnancy, it is essential to switch the patient over to LMWH from 36 weeks of amenorrhoea.
Monitoring and dosage adjustment involves:

• determination of APTT, or, preferably, of anti-Xa activity for patients on UFH
• determination of anti-Xa activity for patients on LMWH
• INR for patients on VKA

For patients on UFH or LMWH, platelet counts should be performed regularly in order to identify type II heparin-induced thrombocytopenia (HIT):

• initial platelet count before the start of treatment
• over the 24 hours following the start of treatment
• twice weekly during the first month of treatment
• once weekly thereafter.

Prevention of thromboembolic accidents involves the use of VKA. Where the latter drugs cannot be used, LMWH or UFH may be given at prophylactic doses. Laboratory monitoring comprises:

• INR for VKA,
• determination of APTT or, preferably, of anti-Xa activity for UFH.

As a general rule, determination of anti-Xa activity is not necessary for patients on prophylactic doses of LMWH.

Monitoring of platelet counts is essential for all patients on UFH and LMWH in order to identify any type II HIT.