Anti-domain 1 of beta2-glycoprotein I aids risk stratification in lupus anticoagulant-positive patients

Lupus anticoagulant (LA) is considered a risk factor for thromboembolism (TE) and adverse pregnancy outcomes (APOs). However, quite a few patients diagnosed with LA positivity do not suffer these adverse events. Further testing of anticardiolipin (aCL), anti-beta2-glycoprotein I (anti-β2GPI) or anti-domain 1 of β2GPI (anti-D1) may help to assess the occurrence risk of TE and APOs. Therefore, we aimed to study how to stratify LA-positive patients. In our study, 167 LA-positive patients were consecutively enrolled from January 2015 to December 2016. Serum aCL and anti-β2GPI (IgG, IgM and IgA) and anti-D1 IgG were simultaneously measured. Among these patients, 114 (68.3%) were followed for an average of 36.5 months for TE and APOs. The outcomes showed that 105 patients experienced TE and/or APOs, and 62 patients were LA carriers. Anti-D1 had good consistency with triple positivity (LA+, aCL+, anti-β2GPI+) (kappa = 0.742). Elevated anti-D1 was related to increased risks for TE [odds ratio (OR) 29.87, 95% confidence interval (CI) 8.05–110.74] and APOs (OR 8.73, 95% CI 3.41–22.31). Area under curve showed that the diagnostic power of anti-D1 for TE and APOs was 0.856 (95% CI 0.743–0.970) and 0.682 (95% CI 0.599–0.765), respectively. Survival analysis revealed that patients with high anti-D1 titres had a high cumulative incidence of APOs (hazard ratio 4.66, 95% CI 1.46–14.87). In conclusion, anti-D1, based on good consistency with triple positivity in LA-positive patients, has a stronger association with TE and APOs and, to some degree, could predict pregnancy outcomes. Therefore, anti-D1 may aid risk stratification in LA-positive patients.