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Antiphospholipid Syndrome

Antiphospholipid Syndrome (APS) is an emerging condition that may underlie more conditions than first perceived. The diverse symptoms of APS include deep venous thrombosis of lower limbs, pulmonary embolism, early and late miscarriages, memory impairment, clinical features of arthritis, livedo reticularis, migraine or epilepsy.1,2

Antiphospholipid Syndrome


APS is a systemic autoimmune disease in which antibodies are directed against phospholipid-protein complexes.2,3

APS is more common in women than men in about a 5:1 ratio. Although the mean onset age of clinical manifestations tends to occur in the middle-age range, it may manifest in children and older patients as well. APS appears to lead directly to a combination of symptoms. Headaches – particularly migraines – going back to childhood and often with family history can be an early feature of APS.2

Recognizing the following clinical manifestations is an important step towards an earlier diagnosis:4

Other common and important signs are:4

  • Thrombocytopenia (30%)
  • Livedo reticularis (24%)
  • Heart valve lesions (12%)
  • Hemolytic anemia (10%)
  • Epilepsy (7%)
  • Myocardial infarction (6%)
  • Leg ulcers (6%)
  • Amaurosis fugax (5%)

Venous and arterial thromboses: the hallmarks of APS1,4

Deep vein thrombosis, sometimes accompanied by pulmonary embolism, is the most frequently reported manifestation in this syndrome (about 39%). Cerebrovascular accidents – either stroke (20%) or transient ischemic attacks (11%) – are the most common arterial thrombotic manifestations.

Fetal and obstetric manifestations5

Fetal and obstetric manifestations of APS are also common with prematurity (28%), early pregnancy loss (18%), preeclampsia (up to 8%).

Diagnosing APS

Currently there are no clinical guidelines for the diagnosis of APS; the only available guidance is the classification criteria which are primarily intended for clinical research. The classification criteria for APS require the identification of at least one clinical and one laboratory criterion.3


Vascular thrombosis

One or more clinical episodes of arterial, venous, or small-vessel thrombosis in any tissue or organ. Thrombosis must be confirmed by objective validated criteria. For histopathological confirmation, thrombosis should be present without significant evidence of inflammation in the vessel wall.

Pregnancy morbidity

One or more unexplained deaths of a morphologically normal fetus at or beyond the 10th week of gestation, OR one or more premature births of a morphologically normal neonate before the 34th week of gestation because of:

  • eclampsia or severe pre-eclampsia, or
  • recognized features of placenta insufficiency
  • three or more unexplained consecutive spontaneous abortions before the 10th week of gestation.

While thrombosis and fetal and obstetric complications are the most recognizable clinical signs of APS; and included in the classification criteria; there is growing evidence of APS presenting with other symptoms.

Some symptoms that should prompt you to consider diagnostic testing for APS include: heart valve lesions; headaches, epilepsy; livedo reticularis; and other autoimmune conditions.3

Laboratory Criteria for APS Classification

The hallmark serological testing result that defines APS is the presence of persistent antiphospholipid antibodies (aPL). To be classified as APS, international consensus of the classification criteria state that a patient must have elevated titers of one of the following antiphospholipid antibody (aPL):3,6

Lupus anticoagulant in plasma


Anticardiolipin antibodies (IgG and/or IgM), considered elevated medium or high titer (>40 GPL or MPL or > 99th percentile) in serum or plasma

Anti-β2-glycoprotein I antibodies (IgG and/or IgM), considered elevated titers a titer > 99th percentile in serum or plasma

These antiphospholipid antibodies are considered to be diagnostic markers and pathogenic drivers of APS.7 The classification criteria for APS states a patient who fulfills clinical criteria can be classified as APS dependent when the patient exhibits a persistently positive aPL result on two or more occasions at least 12 weeks apart.3,8

Allergy Testing


Diagnostic tests give reliable results that support primary care physicians as well as specialists in providing optimal patient management.



  1. Sciascia S, Baldovino S, Schreiber K, et al. Thrombotic risk assessment in antiphospholipid syndrome: the role of new antibody specificities and thrombin generation assay. Clin Mol Allergy. 2016:14:6.  
  2. Hughes RV. Put Hughes Syndrome on Your Radar. The Rhematologist. 2007. http://www.the-rheumatologist.org/article/put-hughes-syndrome-on-your-radar/. Accessed November 2017. 
  3. Miyakis S, Lockshin MD, Atsumi T, et al. International consensus statement on an update of the classification criteria for definite antiphospholipid syndrome (APS). J Thromb Haemost. 2006;4:295-306. 
  4. Asherson RA, Cervera R. The antiphospholipid syndrome: multiple faces beyond the classical presentation. Autoimmun Rev. 2003;2:140-151. 
  5. Marchetti T, Cohen M, de Moerloose P. Obstetrical Antiphospholipid Syndrome: From the Pathogenesis to the Clinical and Therapeutic Implications. Clin Develop Immuno. 2013; Article ID 159124. 
  6. Ortel TL. Antiphospholipid Syndrome Laboratory Testing and Diagnostic Strategies. Am J Hematol. 2012;87(Suppl 1):S75-S81. 
  7. Pericleous C, Ripoll VM, Giles I, et al. Laboratory tests for the antiphospholipid syndrome. Methods Mol Biol. 2014;1134:221-235. 
  8. Devreese KMJ, Pierangeli SS, de Laat B, et al. Testing for Antiphospholipid Antibodies with Solid Phase Assays: guidance from the SSC of the ISTH. J Thromb Haemost. 2014;12:792-795.