1. Vascular thrombosis: ≥1 episode of arterial, venous (excluding superficial veins), or small-vessel thrombosis affecting any tissue or organ confirmed by imaging studies, Doppler study, or histology; histologic features should reveal thrombosis without inflammation of the vessel wall

2. Pregnancy morbidity:

1) ≥1 death of a morphologically normal fetus at ≥10 weeks’ gestation (confirmed with ultrasonography or a direct examination)

2) ≥1 preterm birth of a morphologically normal neonate before 34 weeks’ gestation because of preeclampsia, eclampsia, or severe placental insufficiency

3) ≥3 spontaneous miscarriages <10 weeks’ gestation with no anatomic or chromosomal abnormalities

1. LA detected in plasma on ≥2 occasions at a ≥12-week interval

2. IgG and/or IgM anticardiolipin antibodies present in the plasma or serum in a moderate or high titer (ie, >40 GPL or MPL units or >99th percentile) detected using a standardized ELISA method on ≥2 occasions at ≥12-week intervals

3. Anti–beta2-glycoprotein I antibodies in plasma or serum (in a titer >99th percentile) detected using a standardized ELISA method on ≥2 occasions at ≥12-week intervals

APS is diagnosed when ≥1 clinical and ≥1 laboratory criterion is fulfilled.

A high-risk APLA profile is defined as the presence of laboratory criterion 1; laboratory criteria 2 + 3; or persistently high APLA titers.

a The criteria must not be applied in patients with the onset of clinical manifestations of APS within <12 weeks or >5 years from the first detection of APLAs.