When is testing for antiphospholipid (APL) antibodies indicated?

Updated: Jul 22, 2021
  • Author: Tarek Hammad, MD; Chief Editor: Eric B Staros, MD  more...
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Testing for APL antibodies is most appropriate in patients with suspected APS, such as young people with unprovoked venous or arterial thrombosis, early pregnancy loss, or other pregnancy morbidity, especially those with SLE.

Conversely, it is probably reasonable to test for APL antibodies in young people with provoked venous thrombosis and/or recurrent early pregnancy loss. It may also be prudent to check for these antibodies in asymptomatic patients with unexplained prolonged aPTT discovered incidentally during routine testing, although the presence of APL antibodies in this scenario does not confirm the diagnosis of APS, since the patient is asymptomatic. However, the patient may develop symptoms later, and only then can APS be diagnosed. [1]

Persons with APL antibodies are at risk of developing APS, although the presence of these antibodies might be transient, without any clinical significance. Other manifestations, such as thrombocytopenia, livedo reticularis, heart valvular disease, and nephropathy, may be seen in individuals with APS but are still not part of its diagnostic criteria; the presence of these manifestations, especially in people with thrombosis and/or pregnancy morbidity, should alert the physician to suspect APS and to evaluate for the presence of APL antibodies. [12]

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