Antiphosphatidylserine antibodies as diagnostic indicators of antiphospholipid syndrome

Antiphospholipid syndrome (APS) is an autoimmune condition that is diagnosed by the presence of at least one of the clinical manifestations (thrombosis and/or pregnancy failure) and one of antiphospholipid antibodies (aPL) laboratory tests. The most relevant aPL are lupus anticoagulant (LA), anti-beta2 glycoprotein I (aβ2GPI) and anticardiolipin (aCL). The clinical significance of other antibodies like anti-phosphatidylserine antibodies (aPS) is still under investigation.

The aim of the study was to assess the diagnostic value of aPS antibodies, and to compare their utility to that of other aPL antibodies.

We conducted a prospective observational study consisting of 212 patients with suspected thrombosis, pregnancy failure, or unexplained, prolonged clotting time. Data on demography, clinical presentation and autoantibody levels were assessed. Descriptive analysis, accuracy analysis, sensitivity, specificity, predictive value and likelihood ratio were calculated for aPS in comparison to other aPL.

The diagnostic value of aPS versus other aPL antibodies revealed the high specificity of aPS (87%), with 70% of aPS-positive patients being confirmed APS. When the aPS test was used as a single test, it was effective for detection of confirmed APS cases (p < 0.01). Among 28 confirmed primary APS cases, 75% of patients were positive for aPS (p < 0.003). Moreover, by using aPS we detected three additional confirmed APS cases and another three probable cases.

Our findings reveal a significant association between aPS and APS, especially when used to diagnosis clinical cases with other negative aPL tests. There is an independent association between aPS and primary APS. In addition, these results demonstrated the advantages of using aPS as a diagnostic test for APS.