What is the role of lab tests in the diagnosis of antiphospholipid syndrome (APS)?

Updated: Sep 30, 2018
  • Author: Suneel Movva, MD; Chief Editor: Herbert S Diamond, MD  more...
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Answer

The hallmark result from laboratory tests that defines antiphospholipid syndrome (APS) is the presence of antiphospholipid (aPL) antibodies or abnormalities in phospholipid-dependent tests of coagulation. In addition to the clinical criteria listed in History, at least one of the following laboratory criteria is necessary for the classification of APS:

  • Presence of lupus anticoagulant (LA) in plasma on two or more occasions at least 12 weeks apart (see below)

  • Presence of moderate to high levels of anticardiolipin (aCL) (IgG or IgM) in serum or plasma (ie, > 40 IgG phospholipid units (GPL)/mL or IgM phospholipid units (MPL)/mL or > 99th percentile) on two or more occasions at least 12 weeks apart

  • Presence of moderate to high levels of anti–beta-2 glycoprotein I antibodies (IgG or IgM) in serum or plasma (> 99th percentile) on two or more occasions at least 12 weeks apart


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