Table 2.

Classification criteria for the antiphospholipid syndrome.a

Clinical criteria
1. Vascular thrombosis
≤1 clinical episodes of arterial, venous, or small-vessel thrombosis
2. Pregnancy morbidity
(a) One or more unexplained deaths of a morphologically normal fetus at or beyond the 10th week of gestation
(b) One or more preterm births of a morphologically normal neonate before the 34th week of gestation because of (i) eclampsia or severe preeclampsia or (ii) recognized features of placental insufficiency
(c) Three or more unexplained consecutive spontaneous miscarriages before the 10th week of gestation, with maternal anatomic or hormonal abnormalities and paternal and maternal chromosomal causes excluded
Laboratory criteria
1. Lupus anticoagulant present in plasma, on 2 or more occasions at least 12 weeks apart
2. Anticardiolipin antibody of immunoglobulin (Ig)G and/or IgM isotype in serum or plasma, present in medium or high titer (i.e., >40 IgG antiphospholipid units or IgM antiphospholipid units, or above the 99th percentile), on 2 or more occasions, at least 12 weeks apart
3. Anti-β2-glycoprotein I antibody of IgG and/or IgM isotype in serum or plasma (in titer above the 99th percentile), present on 2 or more occasions at least 12 weeks apart
Antiphospholipid antibody syndrome is present if at least one of the clinical criteria and one of the laboratory criteria are met
  • a From Keeling et al. (5), as adapted from Miyakis et al. (6). Reproduced with permission.