Synonyms: Lupus anticoagulant
Related tests: PTT, anti-cardiolipin
Clinical significance
Lupus anticoagulants (LAC) are a group of antibodies that prolong phospholipid-dependent clotting times. The term “anticoagulant” refers only to the in vitro laboratory test; in the body, lupus anticoagulant actually increases thrombotic events.
The primary form is part of the so-called APS (antiphospholipid syndrome), characterised by recurrent venous and/or arterial thrombosis, repeated miscarriages and antiphospholipid antibodies. The secondary form is found in connective tissue diseases (especially SLE), infections (syphilis, Lyme disease, mycoplasma, viruses), blood disorders and cancers.
Clinical indications
Antiphospholipid antibody syndrome, connective tissue diseases.
Sample type
The patient must have a blood sample taken.
Preparation
You must fast for at least 8 hours; a small amount of water is allowed. You must have been standing or sitting upright for at least 30 minutes.
Notes
Anticoagulants (heparin, warfarin, coumarins) and clotting factor deficiencies can cause false positive results.
A positive LAC result must be confirmed with one or more samples taken at least six weeks after the first.