ABSTRACT
Objective • To investigate diagnostic value of anti-phosphatidylserine/prothrombin antibody (aPS/PT), IgA anti-cardiolipin antibody (aCL), and IgA anti-β2-glycoprotein antibody (aβ2-GPI) in seronegative antiphospholipid (SNAPS). Methods • Serum samples were collected from 86 patients with antiphospholipid (APS) (APS group), 48 patients with SNAPS (SNAPS group), 79 patients with systemic lupus erythematosus (SLE) (SLE group), and 85 healthy donors (healthy control group, HC group) for aPS/PT (IgG and IgM), aCL (IgA) and aβ2-GPI (IgA) detected by ELISA. The sensitivity and specificity of the four antibodies for the diagnosis of SNAPS were calculated, and the ROC curves were analyzed. The correlation between the four antibodies and the clinical manifestations of SNAPS was also analyzed.Results • A total of 25 (52.1%) SNAPS patients were positive in aPS/PT (IgG/IgM), including 29.2% patients positive in aPS/PT (IgG) and 35.4% positive in aPS/PT (IgM). There were 16.7% SNAPS patients positive in aβ2-GPI (IgA), but none was aCL (IgA) positive. The positive rates of aPS/PT (IgG and IgM) and aβ2-GPI (IgA) were statistically higher in SNAPS group than those in HC group (P=0.000). The area under curve (AUC) of aPS/PT (IgG) (AUC=0.753) for SNAPS diagnosis was the biggest among the four antibodies, and the second was aβ2-GPI (IgA) (AUC=0.725). A positive correlation was found in SNAPS group between presence of venous thrombosis and aPS/PT (IgG) (OR=5.54, 95% CI 1.67-17.33, P=0.003) or aβ2-GPI (IgA) (OR=3.43, 95% CI 0.86-11.53, P=0.041), and also found between pregnancy loss and aPS/PT (IgM) (OR=5.11, 95% CI 1.31-21.29, P=0.004). Conclusion • aPS/PT (IgG/IgM) and aβ2-GPI (IgA) can be used as potential complementary indicators for laboratory diagnosis of SNAPS, and aPS/PT (IgG/IgM) is also valuable for clinical evaluation of the risk of thrombosis and pregnancy loss in SNAPS patients.