Antiphosphatidylserine/prothrombin antibodies as biomarkers to identify severe primary antiphospholipid syndrome.

BACKGROUND: Anti-phosphatidylserine/prothrombin (aPS/PT) antibodies have begun to be considered potentional biomarkers for antiphospholipid syndrome (APS). This cohort study investigate the role of aPS/PT antibodies as a risk factor for severe APS by evaluating the association between those antibodies and clinical/laboratory profiles of APS. METHODS: Plasma/serum samples from 197 APS patients, 100 healthy subjects and 106 patients with autoimmune diseases were collected. IgG/IgM aPS/PT antibodies were assayed using commercial ELISA kit. RESULTS: Prevalences of IgG and IgM aPS/PT (p<0.0001 and p=0.0009, respectively) and their titres (p<0.0001 and p=0.0002, respectively) were significantly higher in thrombosis/pregnancy group with respect to pregnancy morbidity alone. Prevalences of IgG and IgM aPS/PT (p<0.0001 and p=0.0004, respectively) and their mean levels (p=0.0001 for both) were significantly higher in the prematurity linked to life-threatening obstetric complications group with respect to miscarriage group. There was a significant relationship between IgG and IgM aPS/PT (p=0.001 and p=0.0002) and their mean levels were higher (p=0.0004 and p=0.0002, respectively) in the thrombotic microangiopathy group, considered a milestone manifestation of catastrophic APS. The relationship between IgG and IgM aPS/PT was significant and mean levels were higher in triple positive antiphospholipid antibody patients than in double and single positivity ones (p<0.0001 for all). CONCLUSIONS: APS/PT antibodies were associated to severe thrombosis, severe pregnancy complications inducing prematurity, and vascular microangiopathy, all generally associated to high risk APS forms requiring strong therapy.