David L. McGlasson, MS, MLS(ASCP)
Lupus Anticoagulants/Antiphospholipid Antibodies/Antiphospholipid Antibody Syndrome
The late Douglas A. Triplett, MD, PhD, who was a colossal figure in the field of Coagulation, paraphrased Winston Churchill in describing a lupus anticoagulant/antiphospholipid antibody as: “a riddle, wrapped in a mystery, inside an enigma.” In other words, a difficult problem to identify and analyze as you will see in the following communication.
The inhibitors originally described as lupus anticoagulants (LA) are now recognized to be part of a more diverse group of inhibitors collectively referred to as antiphospholipid antibodies (APA). They are immunoglobulins of the IgG, IgM, or IgA class that are directed against the protein component of protein-phospholipid complexes. In vivo, APAs may be associated with a thrombotic tendency; in vitro, they prolong phospholipid-dependent clotting assays.
The diagnosis of antiphospholipid antibody syndrome (APS) requires the demonstration of (1) an abnormality of phospholipid-dependent coagulation reactions, (2) an abnormality that results from the presence of an inhibitor rather than a factor deficiency, and (3) the phospholipid-dependence of the inhibitor. These LA tests are used to evaluate (1) patients with history of recurrent abortions, venous or arterial thrombosis, and (2) as part of the evaluation of autoimmune disorders, and (3) potential cause for elevated APTT (with or without elevated PT).1,2
COVID-19 AND ANTI-PHOSPHOLIPID ANTIBODIES: Are they connected with thrombosis seen in previous findings?
Previous CLOT CLUB blog posts discussed the markers that are found in the COVID-19 hypercoaguable state that develop in subjects who contract this disorder. Due to the prolonged APTT, there was a suspicion of decreased coagulation factors and the presence of anti-phospholipid antibodies syndrome (aPS). However, there was some question that they were transient.
Results seen in small studies have been questionable, and if the positive findings are truly relevant to the thrombotic conditions found in the COVID-19 subjects. Could they be part of a pattern caused by the infectious disease, as have been seen in: VDRL, HIV, Lyme disease, Epstein-Barr and cytomegalovirus, Gulf War syndrome, Hepatitis C, and others which can drive anticardiolipin antibody (ACA) positivity? If there is no thrombotic disorder, they can mistakenly be given a diagnosis of aPS. Subjects with aPS have β2GPI bound to cardiolipin. Many of the new assays for ACA antibodies include a combination of both the ACA+β2GPI.
In one study the authors ran a panel of testing on 31 subjects that included lupus anticoagulants (LA), anticardiolipin antibodies (ACA) IgG, IgM, anti-beta2-glycoprotein I antibodies (aβ2GPI) IgG/IgM and non-criteria (anti-prothrombin/phosphatidyl serine (aPS/PT), aCL and a aβ2GPI IgA testing. All test subjects were critically ill with COVID-19. The authors of the study wanted to check the association of the testing with the thrombotic state that is seen in COVID-19.
All the testing on the individual patients were collected in the ICU at a specific time and then, for some patients, one month later. The results of 31 original patients that were available are as follows: 16 single LAC positive, two triple positive, one double positive, one single aCL out of 22 without thrombosis were aPL positive with two triple positives. Nine out of 10 retested LAC positive were negative after one month as was the double positive finding. Seven patients were aPS/PT positive associated to LAC. Three were aCL and aβ2GPI IgA positive.1
Their findings support the frequency of a single LAC positivity during the acute phase of the infection observed in COVID-19 onset, but not necessarily with thrombotic complications. Triple aPL positivity and elevated aCL/aβ2GPI titers are rare. The second testing gives the premise that aPL is, for the most part, transient. Obviously, further studies are needed.1
A second study used only solid phase testing, such as ELISA and chemiluminescence, as functional coagulation assays can be affected by elevated levels of C-reactive protein and anticoagulant therapy. The study used aCLs IgG, IgM, aβ2GPI, and anti-phosphatidylserine/prothrombin (aPS/PT). Serum from 122 subjects with severe COVID-19 symptoms were used in this protocol. Out of this cohort, 16 had serious thrombotic issues. In this group aβ2GPI IgG/IgM/IgA were the most frequent findings: 15.6/9.0/6.6% while aCL IgG/IgM were detected in 5.7/6.6% by ELISA techniques1
When the chemiluminescence were run on the same specimens, there was no clinical or statistical significance seen. The aPS/PT IgG/IgM were detectable in 2.5/9.8% by ELISA. No association between thrombosis and aPL were detected. The reactivity against domain 2 and 4,5 of β2GPI only was found in 3/58 or 5.2% tested for each domain and did not match up with aCL/ aβ2GPI without a correlation of thrombosis.
The findings of this study show the aPL has a low prevalence in subjects afflicted with COVID-19 and are not affected with major thrombotic episodes. In COVID-19 subjects the aPL are primarily affecting the β2GPI but display an epitope affinity different from the antibodies seen in patients with “true antiphospholipid syndrome.2 Further studies are needed to confirm these findings.
- Devreese KMJ. Linskens EA, Benoit D et al: Antiphospholipid antibodies in patients with COVID-19: a relevant observation. J Thromb Haemost 2020 doi:10.1111.JTH.14994.
- Borghi MO, Beltagy A, Garrata E. et al: Anti-Phospholipid antibodies in COVID-19 Are Differerent From Those Detectable in the Anti-Phospholipid Syndrome. Frontiers in Immunology 2020 11:Article 58:241.