Lupus Anticoagulant Study (Blood)

Diagnostic Use

Lupus anticoagulant study is used to detect lupus anticoagulant (LA) in the blood. LA is an autoantibody that can be transient with no clinical significance or can lead to Antiphospholipid Syndrome with an increased risk of arterial or venous thromboembolism. LA testing may be used to help determine the cause of:

• Arterial or venous thromboembolism.
• Recurrent miscarriages.
• An unexplained prolonged APTT test, as part of the workup to determine whether the prolonged APTT is due to a specific inhibitor, such as an antibody against a specific coagulation factor, or to a nonspecific inhibitor like lupus anticoagulant.

Serial LA testing may also be used:

• Along with tests for anticardiolipin antibody and anti-beta2-glycoprotein-1 to diagnose antiphospholipid syndrome (APS). The laboratory criteria for the diagnosis of APS requires the same abnormal laboratory test/s (lupus anticoagulant, anticardiolipin antibodies and anti-beta2 antiglycoprotein-1) to remain positive at least three months apart.
• To determine whether the lupus anticoagulant is temporary (transient) or persistent.

Anticoagulation can interfere with LA testing, and testing would ideally be performed when the patient is not receiving anticoagulation therapy.

LA cannot be measured directly and there is no single test or standardized procedure to detect the presence of LA in the blood. A series of tests is used to confirm or rule out the autoantibody. A Lupus Screen includes APTT, PTT-LA, dilute Russell Viper Venom Time and correction studies.

Interpretation

Lupus anticoagulants may occur in individuals with autoimmune diseases, infections including HIV, inflammation, cancers, and in people who take certain medications, such as phenothiazines, penicillin, quinidine, hydralazine and procainamide.

Patients on heparin including LMWH or non-warfarin anticoagulant therapy such as direct thrombin inhibitor (e.g. dabigatran) or direct anti-Xa drugs (e.g. rivaroxaban) will have false-positive results for lupus anticoagulant. Warfarin therapy may also cause false test results if levels of coagulation factors II, VII, IX and X are significantly decreased. If possible, lupus anticoagulant testing should be done prior to the start of anticoagulation therapy or after cessation. If testing cannot be deferred then please state which anticoagulant the patient is or has recently been receiving.

For someone with a confirmed lupus anticoagulant, the usual APTT for heparin monitoring may be unreliable, so heparin assay with anti-Xa method should be used.

Reference Intervals