Antiphosphatidylserine/prothrombin (aPS/PT) antibodies may be a useful serological tool to diagnose and phenotypically characterize patients with antiphospholipid syndrome (APS), according to a study published in Thrombosis Research.

Researchers examined the prevalence of various aPS/PT antibodies and their association with other antiphospholipid antibodies and with different APS clinical phenotypes. They assessed 95 patients with primary APS, thrombocytopenia, or hemolytic anemia who met the Sydney APS classification criteria. In the cohort, 70.5% of the patients were female, with a mean age of 44.4 years and median disease duration of 7.3 years. The key clinical features were thrombosis (77.8%), hematologic involvement (50.5%), and obstetric complications (25.2%).

The researchers tested anticardiolipin, anti-beta-2glycoprotein-I, and aPS/PT antibodies (both immunoglobulin G [IgG] and immunoglobulin M [IgM] isotypes) and lupus anticoagulant. They found that 61% of patients had IgG aPS/PT antibodies and 60% had IgM aPS/PT antibodies. In addition, patients who were lupus anticoagulant-positive had a higher prevalence (P =.0001 for IgG; P =.001 for IgM) and higher titers (P =.0001 for both) of both aPS/PT antibodies.

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IgG aPS/PT antibodies were associated with thrombosis (odds ratio [OR], 8.6) and pure hematologic features (OR, 0.2); IgM anti-beta-2glycoprotein-I antibodies were associated with an increased risk for both hematologic involvement (OR, 7.9) and thrombotic involvement (OR, 7.4).

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The authors concluded that “patients with hematologic APS had a lower prevalence of IgG aPS/PT … and that their IgG aPS/PT titers were 5-fold lower” compared with patients with thrombotic APS, indicating that patients with different clinical phenotypes of APS also demonstrate different serological profiles.


1. Núñez-Álvarez CA, Hernández-Molina G, Bermúdez-Bermejo P, et al. Prevalence and associations of anti-phosphatidylserine/prothrombin antibodies with clinical phenotypes in patients with primary antiphospholipid syndrome aPS/PT antibodies in primary antiphospholipid syndrome [published online December 28, 2018]. Thromb Res. doi: 10.1016/j.thromres.2018.12.023