Table 1.

Description of aPL antibody and related tests

TEST	ACTIVITY
Routine tests
Anticardiolipin antibodies	Originally thought to measure antibodies against this phospholipid, but now understood to detect phospholipid binding proteins. Cardiolipin is present in intracellular membranes.
Anti-β2GPI antibodies	Measure antibodies against this phospholipid-binding.
Lupus anticoagulant test	Measures antibody-mediated interference in assembly of blood coagulation complexes on phospholipid. Surrogate test for high affinity/avidity aPL antibodies.
Other tests
Antiphosphatidyl-serine antibodies	Measures antibodies bonding to this phospholipid that may be more biologically active than cardiolipin because it is expressed on cytoplasmic membranes.
Anti-domain1 IgG	Detects antibodies that bind to this aminoterminal domain of β2GPI.
Anti-annexin A5 antibodies	Measures antibodies that bind to this phospholipid binding protein.
Annexin A5 resistance assay	Detects antibodies that bind with high affinity and interfere with the anticoagulant activity of this protein.