**4. Thrombotic and obstetric risk assessment**

Risk stratification is a major challenge in the management of patients with APS, and a possible role of aPL as a risk or even prognostic factor for arterial/venous thrombosis and miscarriages has been intensively discussed [27, 29]. Single, double, and triple aPL positivity is not uncommon in patients with APS, and such multiple positivity is usually associated with a higher risk for the occurrence or recurrence of thrombotic or obstetric adverse event [30, 31]. Recently, two research groups proposed a quantitative index to quantify the likelihood of thrombosis in APS. One included the aPL profile, and the aPL score (aPL-S) [27], whereas the other included both aPL and conventional prothrombotic risk factors, the global APS score (GAPSS) [28]. Both groups included LA and IgG and IgM isotypes of aCL, anti-β2GPI and aPS/PT.

In contrast to risk stratification for thrombotic events, which has been well studied in aPL-positive patients, studies assessing the risk for obstetric complications are scarce. A recent study examined different scoring systems after 2 years of systematic review [9]. They showed that all non-criteria aPL, including IgA aCL, IgA anti-β2GPI, and IgA/IgG aPS/PT were significantly associated with both thrombosis and obstetric complications. They proposed a novel quantitative scoring to evaluate the risk of adverse pregnancy events in aPL-positive patients, namely the obstetric risk score—ORS. The ORS showed much higher diagnostic accuracy for obstetric complications compared with any single aPL measure.
