What is an Antiphospholipid (APL) Antibody test?

Antiphospholipid antibodies are a type of autoantibodies that are produced against body’s own phospholipids (a lipid-containing a phosphate group in its molecule). Since phospholipids play an important role in the formation of blood clots, people with APL antibodies have a high risk of blood clots, which in turn increases the risk of stroke, heart attack and miscarriage.

Several tests are available to check for the presence of specific types of APL antibodies in the bloodstream. Some of these include:

  • Cardiolipin antibodies (anticardiolipin antibodies) test: This test helps detect the most common APL antibodies that are formed against cardiolipin, a type of phospholipid present on the cell membrane of blood platelets
  • Lupus anticoagulant assays: Lupus anticoagulant is a specific type of APL antibody that is usually present in people with lupus. Lupus anticoagulant assays detect the presence of these antibodies in the bloodstream of the patient. These tests include dilute Russell viper venom time (dRVVT), activated partial thromboplastin time (aPTT), kaolin (or silica) clotting time and PTT mixing tests or prolonged PTT test
  • Beta-2 glycoprotein 1 antibody test: This test is used to detect the presence of beta-2 glycoprotein 1 type of APL antibodies

Some conditions that lead to the formation of APL antibodies are:

Hughes syndrome or APL antibody syndrome (APS) is an autoimmune disorder, which leads to thickening of the circulating blood. The immune system produces APL antibodies, which causes platelets to clump, leading to increased blood clotting.

  1. Why is an Antiphospholipid (APL) Antibody test performed?
  2. How do you prepare for an Antiphospholipid (APL) Antibody test?
  3. How is an Antiphospholipid (APL) Antibody test performed?
  4. What do Antiphospholipid (APL) Antibody test results indicate?

An APL antibody test is used to determine the cause of

  • Unexplained blood clot formation (excessive clotting)
  • Recurrent miscarriages
  • Low platelet count (thrombocytopenia)
  • Prolonged PTT

Blood clots due to APL antibodies can also cause

 Common symptoms that indicate a need for APL test include:

No special preparation is needed for APL test.

It can be done at any time of the day without fasting. Some medicines can alter the results of this test; hence, it is necessary to inform your doctor if you are on any medications or supplements. 

Also, it is best if you wear a half-sleeved shirt while going for the test as it helps ease blood withdrawal.

A blood sample will be drawn from a vein in your arm using a sterile needle. Your healthcare provider will first clean the needle injection site with alcohol before inserting the needle into the vein.

After sample withdrawal, the injection site is pressed firmly, and a cotton ball or gauze pad is placed over it. The collected blood sample is further sent for examination.

  • A negative result indicates the absence of APL antibody
  • Low to moderate levels do not necessarily indicate the presence of autoantibodies. It can also be caused by some drug or infection or ageing factors. Hence, the clinical signs and symptoms must be considered to confirm the diagnosis
  • Moderate to high level of a particular APL antibody will only indicate the presence of that particular antibody. It needs to be tested again after 12 weeks for confirmation

However, none of these tests indicate the complications and severity of the condition. Some patients may have recurrent symptoms while others may be asymptomatic.

Transient APL antibodies can be seen in people with autoimmune disorders, inflammation, infections or cancer.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.  

References

  1. Bustamante JG, Singhal M. Antiphospholipid Syndrome (Antiphospholipid Antibody Syndrome, APS, APLS) [Updated 2018 Dec 29]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan
  2. Lupus Foundation of America [internet]. Washington D.C. (U.S.); Antiphospholipid antibody syndrome
  3. Merck Manual Professional Version [Internet]. Kenilworth (NJ): Merck & Co. Inc.; c2019. Antiphospholipid Antibody Syndrome (APS)
  4. Johns Hopkins Medicine [Internet]. The Johns Hopkins University, The Johns Hopkins Hospital, and Johns Hopkins Health System; Antiphospholipid Antibodies
  5. Gómez-Puerta JA, Cervera R. Diagnosis and classification of the antiphospholipid syndrome. J Autoimmunity 48-49:20-25.
  6. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; Antiphospholipid Antibody
  7. Tripodi A. (2007) Laboratory testing for lupus anticoagulants: A review of issues affecting results. Clin Chem 53:9, 1629-1635.
  8. Bertolaccini ML, et al (2014). 14th International Congress on Antiphospholipid Antibodies Task Force. Report on antiphospholipid syndrome laboratory diagnostics. Autoimmun Rev 13(9):917-930.
  9. Erkan D, Salmon JE. The role of complement inhibition in thrombotic angiopathies and antiphospholipid Syndrome. Turk J Haematol. 2016;33(1):1-7.
  10. Lopes MRU, Danowski A, Funke A, Rêgo J, Levy R, Andrade DCO de, et al. Update on antiphospholipid antibody syndrome. Revista da Associação Médica Brasileira. 2017;63(11):994-999.
  11. Better health channel. Department of Health and Human Services [internet]. State government of Victoria; Hughes syndrome
  12. Health direct [internet]: Department of Health: Australian government; Antiphospholipid syndrome (APS)
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