The diagnostic and prognostic values of non-criteria antiphospholipid antibodies in obstetric antiphospholipid syndrome

Obstetric antiphospholipid syndrome (OAPS) is a subtype of antiphospholipid syndrome associated with adverse pregnancy outcomes. Non-criteria antiphospholipid antibodies (aPLs) were focused in recent years, but the diagnostic and prognostic values of them in OAPS were rarely explored. A single-center retrospective study enrolled 283 pregnant women with history of pregnancy loss at an university hospital in sourthwest China. All participants were tested for criteria and non-criteria aPLs, including anticardiolipin antibodies (aCL) IgA, anti-β2 glycoprotein I antibodies (aβ2GPI) IgA, anti-β2 glycoprotein I domain 1 (aβ2GPID1) IgG and anti-phosphatidylserine/ prothrombin (aPS/PT) IgG/IgM. The subsequent pregnancy outcomes were followed up. The prevalence of non-criteria aPLs were compared among patients who classified into OAPS, non-criteria OAPS (NOAPS) and control groups. Receiver operating characteristic (ROC) curve, area under the curve (AUC), sensitivity, specificity and odds ratios (OR) with 95% confidence interval (CI) were calculated to estimate diagnostic and prognostic values of these non-criteria aPLs for OAPS and NOAPS patients. The positive rate of aPS/PT IgM was higher in OAPS (44.4%) compared to NOAPS (18.1%) and controls (3.5%) (P < 0.001). aPS/PT IgM presented moderate diagnostic performance in OAPS (AUC = 0.72) but poor performance in NOAPS (AUC = 0.57). Parallel testing of lupus anticoagulant (LAC) and aPS/PT IgM enhanced sensitivity in diagnosing OAPS, and improved accuracy and sensitivity in diagnosing NOAPS. After adjustment, aPS/PT IgM remained a significant predictor of both overall adverse pregnancy outcomes (OR = 3.85, 95% CI: 1.10–13.40, P = 0.03) and early pregnancy loss before 10 weeks (OR = 4.87, 95% CI: 1.03–23.05, P = 0.04) in OAPS patients. However, due to the extremely low positive rates, we did not observe clinical significance of aCL IgA, aβ2GPI IgA, aß2GPID1 IgG and aPS/PT IgG. aPS/PT IgM exhibits diagnostic and prognostic value for OAPS patients. For NOAPS patients, parallel testing of aPS/PT IgM and LAC may improve diagnostic performance.