The present invention provides methods for diagnosing and/or monitoring thrombophilic disease in a patient that can result from the antiphospholipid antibody syndrome (aPL syndrome). The methods of the invention are premised on the inhibition of binding of an anticoagulant protein, annexin, preferably annexin-V, to phospholipids by antiphospholipid (aPL) antibodies in a patient blood sample.