Tetra positive thrombotic antiphospholipid syndrome: Major contribution of anti‐phosphatidyl‐serine/prothrombin antibodies to lupus anticoagulant activity

Abstract

Background:The concurrent presence of lupus anticoagulant, anticardiolipin, and anti β2-glycoprotein I antibodies (triple positive profile) identifies patients at high risk of thromboembolic events. These patients are also positive for anti-phosphatidylserine/prothrombin antibodies (tetra-positive profile).Objective: Understand which antibody among anti-β2-glycoprotein I and anti-phosphatidyl-serine/prothrombin is responsible for lupus anticoagulant activity.Patients/Methods: Affinity purified anti-β2-glycoprotein I antibodies from plasma of 14 tetra-positive patients spiked into normal pooled plasma were tested. Results and Conclusions:Anti-β2-glycoprotein I antibodies did not prolong the diluted Russell viper venom time and silica clotting time (median ratio 0.98, interquartile ratio[IQR] 0.9-1.06; and 1.0, IQR 0.91-1.03, respectively). Anticoagulant activity remained in the flow-through that was deprived of anti-β2 glycoprotein I antibodies (median ratio 1.88, IQR 1.58-2.77; and 1.75, IQR 1.17-2.9, respectively). This material was loaded on size-exclusion chromatography Sephacryl S-300 column and showed that anticoagulant activity and anti-phosphatidyl-serine/prothrombin antibodies coeluted in the same fractions. Besides, the flow through was poured into a prothrombin affinity column. Protein yield in three patients ranged from 54 to 91 μg/mL and showed strong positivity in phosphatidyl-serine/prothrombin ELISA. The affinity purified material prolonged the coagulation time of normal pooled plasma: the diluted Russell viper venom ratio in the three patients was 2.09, 1.21, and 1.35; that of silica clotting time was 2.05, 1.5, and 2.13. In conclusion, under the assay conditions used, anticoagulant activity in tetra-positive antiphospholipid syndrome patients may largely be attributable to anti-phosphatidyl-serine/prothrombin antibodies.

Anti-Phospholipid Antibodies in COVID-19 Are Different From Those Detectable in the Anti-Phospholipid Syndrome

“…This indicates that aPS/PT are not responsible for the prolongation of aPTT nor are predictors of adverse clinical outcomes. Furthermore, in contrast to what we would have expected in APS ( 32 ), we found no associations between the presence of aPS/PT, aCL, and anti-β 2 GPI antibodies. This data is in line with the unusual epitope specificity of anti-β 2 GPI antibodies documented in Figure 2 , supporting the hypothesis that aPL found in COVID-19 patients are different from aPL found in APS patients.…”

Trial of Rivaroxaban in AntiPhospholipid Syndrome (TRAPS): Two‐year outcomes after the study closure

“…It should be underlined that different antiphospholipid (aPL) laboratory profiles are not equivalent in predicting future thromboembolic events and that their clinical relevance is quite different. Triple positivity (in most cases tetra positivity 18 ) is always confirmed after 12 weeks, whereas single test positivity is confirmed after 12 weeks in <50% of cases 19 . All 14 participating centers confirmed the presence of triple‐positive aPL profiles during the 2‐year follow‐up after TRAPS closure.…”

“…17 It should be underlined that different antiphospholipid (aPL) laboratory profiles are not equivalent in predicting future thromboembolic events and that their clinical relevance is quite different. Triple positivity (in most cases tetra positivity 18 ) is always confirmed after hypertension. 20,21 Moreover, all 14 catastrophic APS seen in the Padua hospital were triple-positive patients.…”

Additional laboratory tests to improve on the diagnosis of antiphospholipid syndrome: Response from Pengo

“…[1][2][3] Testing for lupus anticoagulant (LA) is mandatory to detect triple-pos- with APS and triple positivity are also positive in aPS/PT (tetra-positive aPL) 7 and that aPS/PT more than aβ2GPI is responsible for LA activity in these patients. 8 Finally, if aCL and aβ2GPI antibodies are of immunoglobulin G (IgG) isotype I would measure IgG aβ2GPI/domain 1 antibodies that are associated to thromboembolic events. 9 A tentative decision-making scheme to choose the appropriate anticoagulant treatment in young patients with venous thromboembolism is presented in Figure 1.…”

“…At the same time, I would check anti–phosphatidyl‐serine/prothrombin (aPS/PT) antibodies that can be used as a surrogate test for LA. We have recently shown that most patients with APS and triple positivity are also positive in aPS/PT (tetra‐positive aPL) 7 and that aPS/PT more than aβ2GPI is responsible for LA activity in these patients 8 . Finally, if aCL and aβ2GPI antibodies are of immunoglobulin G (IgG) isotype I would measure IgG aβ2GPI/domain 1 antibodies that are associated to thromboembolic events 9 …”