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Antiphospholipid Syndrome

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The goals of testing are to diagnose APS and to distinguish it from other causes of symptoms and complications. Not everyone who has antiphospholipid antibodies has symptoms or complications. Therefore, a diagnosis of APS is made based upon both clinical signs and the presence of the autoantibodies. At least one clinical sign and one autoantibody must be present.

The following consensus guidelines are used:

Revised Classification Criteria for the Antiphospholipid Antibody Syndrome*
Clinical criteria Laboratory criteria

Vascular thrombosis:

  • One or more confirmed clinical episodes of a blood clot occurring in an artery, vein or small blood-vessel in any tissue or organ validated by imaging studies or tissue biopsy

Pregnancy complications: 

  • One or more unexplained deaths of a physically normal fetus at or after the 10th week of pregnancy
  • One or more premature births of a physically normal newborn at or before the 34th week of pregnancy due to pre-eclampsia, eclampsia, or a placenta that does not function properly
  • Three or more unexplained consecutive miscarriages before the 10th week of pregnancy

Positive test for one of the autoantibodies on 2 or more occasions at least 12 weeks apart:

*Established in 2006 by the 11th International Congress on Antiphospholipid Antibodies

Laboratory Tests

Blood tests that are used to detect the presence of autoantibodies include:

Other tests may be ordered to evaluate blood clotting and blood cells. They may include:

Non-Laboratory Tests

Imaging scans may be performed to confirm the presence of and locate a blood clot, to evaluate organ damage, and, during pregnancy, to monitor a fetus. These may include:

  • CT scan
  • MRI
  • Ultrasounds to detect blood clots or to monitor fetal health and growth
  • Echocardiograph to detect heart valve abnormalities that can occur with APS

For more on these, see the web site

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