There are good tests that specifically measure autoantibodies against the most common phospholipid protein targets seen in antiphospholipid syndrome (APS). These tests include:
- Anti-cardiolipin IgG
- Anti-cardiolipin IgM
- Beta-2 glycoprotein 1 IgG
- Beta-2 glycoprotein 1 IgM
But there are also less specific coagulation tests (clotting tests) that are used to help uncover a lupus anticoagulant. Often, LAC is discovered when a patient has a prolonged PT or aPTT but no factor deficiency. So there are two scenarios to consider:
The first is when a patient presents with recurrent thrombi or fetal loss. Specific antibodies to cardiolipin and beta-2 glycoprotein 1 will be ordered in this scenario.
The second scenario is when a patient has an unexplained prolonged clotting time in vitro (in the lab) but has no bleeding issues. In this latter case, the LAC is often discovered as an incidental finding. When present, LAC will inhibit all the contact activation pathway factors (VIII, IX, XI, and XII). Remember that LAC will cause increased clotting in vivo (in the patient) but decreased clotting in vitro (in lab tests).
