Studies of specific markers for in vivo activation of coagulation in patients with antiphospholipid antibodies (aPL) are very rare. Increased levels of prothrombin fragment F1+2 (F1+2) in patients with APS were reported.
Our aim was to ascertain the relationship of F1+2 plasma levels with positive anticardiolipin (aCL) and anti-β2-glycoprotein I (anti-β2-GPI), and to evaluate the effect of treatment on F1+2 values in patients with APS.
A total of 205 samples from 177 patients with suspected or confirmed connective tissue disease without APS, and 15 samples from nine patients with APS receiving anticoagulant (n = 8) or antiplatelet (n = 1) therapy were tested for plasma F1+2 values (Enzygnost F1+2 micro, Behring, Germany), aCL (IgG, IgM) and anti-β2-GPI (IgG, IgM, IgA), all using in-house ELISAs.
Elevated values of F1+2 were statistically significantly associated with medium/high positive results for at least one isotype of aCL (P = 0.027), anti-β2-GPI (P = 0.019) and aCL and/or anti-β2-GPI (P = 0.014; Table 1). Furthermore, the mean level of F1+2 was significantly higher in patients with medium/high aCL or anti-β2-GPI than in those with negative/low positive aCL and anti-β2-GPI (P = 0.035). In all 15 plasma samples from APS patients, normal levels of F1+2 were measured during treatment.
Table 1. Association of F1+2 with aCL and/or β 2-GPI
Our study showed a significant association of aCL and anti-β2-GPI with elevated levels of F1+2 in patients without APS not receiving anticoagulant or antiaggregation therapy. aPL are believed to be among the important causes of hypercoagulable state in those patients. Furthermore, plasma values of F1+2 could be a very useful indicator of successful treatment in APS patients.