WHAT IS CIRCULATING ANTICOAGULANT (CAC, LUPUS ANTICOAGULANT) TEST?
Circulating anticoagulants (CACs) and lupus anticoagulants develop spontaneously or are acquired in association with autoimmune diseases or certain medication exposure. Clients with systemic lupus erythematosus, malignancies such as multiple myeloma, or chronic inflammatory diseases such as ulcerative colitis and rheumatoid arthritis as well as renal transplant recipients are known to develop these antibodies. CACs may also develop during complications postpartum or in clients taking chlorpromazine or similar drugs. In the laboratory, they prolong the PT (prothrombin time), PTT (partial thromboplastin time), or APTT (activated partial thromboplastin time), or all of these. CACs are detected by a test called a “mixing study,” in which normal plasma is added to client plasma, and the PT, PTT, or APTT is repeated. Failure to correct the clotting to normal is a positive test. Additional tests are used to determine whether the CAC is a specific factor inhibitor or a lupus anticoagulant.