LA is a series of tests that detects the presence of autoantibodies in the blood. Associated with blood clot formation, the tests are used to identify the causes of an unexplained blood clot (thrombosis) in a vein or artery or recurrent miscarriages in a woman. It is also used to determine the cause of a prolonged partial thromboplastin time. LA testing aids in identifying if a prolonged PTT is because of a specific inhibitor, like an antibody against a specific coagulation factor, or because of a nonspecific inhibitor like the lupus anticoagulant, or due to deficiency in coagulation factor(s). LA testing is also used alongside tests for cardiolipin antibody and anti-
I to diagnose antiphospholipid syndrome (APS) as well as factor V Leiden, antithrombin, or
and S to aid in diagnosing an excessive clotting disorder (thrombophilia). It is also helpful in determining whether the lupus anticoagulant is temporary or persistent.
Since there is no standardized testing for LA and it can not be measured directly, there are a series of tests that are used to confirm or rule it out. The process is twofold. First, an LA screen is used, which consists of two tests used to detect LA – the DRVVT and PTT-LA. After this, follow-up testing is used to confirm whether the patient has LA in their blood or not. This may consist of a mixing study which consists of mixing an equal volume of patient plasma with normal pooled plasma, and a
or DRVVT being performed on this mixture. Or it can consist of a correction/neutralization where an excess of phospholipids is added to a patient sample, and a PTT-LA or DRVVT is performed on it.