Most of the carriers/patients triple positive for antiphospholipid antibodies (Lupus Anticoagulant-LAC, IgG/IgM anticardiolipin-aCL and anti ß2-Glycoprotein I-aß2GPI antibodies) are tetra-positive being positive for anti-phosphatidyl-serine/prothrombin antibodies (aPS/PT). The relationship between aPS/PT titer, LAC potency and resistance to activated Protein C (aPC-R) has not been investigated. Aim of this study was to clarify the mutual interdependence of these parameters in tetra-positive subjects.
Twenty-three carriers and 30 patients with Antiphospholipid Syndrome (APS), none of whom were being treated with anticoagulants, and 30 age- and sex-matched controls were studied. Detection of aPS/PT, LAC and aPC-R in each individual was performed with established methods in our laboratory. Carriers and patients were positive for IgG or IgM aPS/PT or for both isotypes without significant difference. Since both IgG and IgM aPS/PT have anticoagulant activity, we used the sum of their titers (total aPS/PT) for the correlation studies.
Total aPS/PT exceeded that in controls in all individuals studied. There was no difference in total aPS/PT titers (p=0.72), LAC potency (p=0.56) and aPC-R (p= 0.82) between antiphospholipid antibody (aPL)-carriers and APS patients . There was a significant correlation between total aPS/PT and LAC potency (r=0.78, p<0.0001) and between total aPS/PT titers and aPC-R (r=0.80, p<0.0001). LAC potency also was correlated significantly with aPC-R (r=0.72, p<0.0001).
This study shows that there is interdependence between anti PS/PT, LAC potency and aPC-R.

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