Test code links throughout this Guide refer to the corresponding test in the User's Guide. Antiphospholipid antibody is a generic term that operationally describes antibodies that recognize negatively charged phospholipids. The most commonly tested phospholipid is cardiolipin. Antiphospholipid antibodies associated with rheumatic illness tend to have IgG more than IgM isotype, both IgG2 and IgG4 subclasses, and have high titer and high avidity.
Antibodies associated with infections, drugs, or neoplasia tend to have IgM more than IgG isotype.
Anticardiolipin antibodies are also associated with the antiphospholipid syndrome, which is characterized by venous and arterial thrombosis, thrombocytopenia, cerebral vascular accidents, and recurrent fetal miscarriage. Results in the inconculsive range and positive results for IgM only should be carefully interpreted. Syndrome of the black swan. Harris EN, et al. Kalunian KC, et al.