What it measures
Lupus anticoagulant is a type of antiphospholipid antibody. The lab finds it by the way it makes clotting tests take longer, so the test is a set of clotting times run with and without extra phospholipid. Despite the name, it is linked with clots forming in the body, and many people who have it do not have lupus.
Why people test it
- Measured after an unexplained blood clot, such as a clot in a leg or lung.
- Checked after repeated miscarriages or some other pregnancy problems.
- Part of the antiphospholipid screen, with cardiolipin and beta-2 glycoprotein I antibodies.
- A positive result is usually repeated at least 12 weeks later to confirm it.
Typical range
The result is reported as detected or not detected (positive or negative), often with the clotting-time ratios behind it. Labs use their own methods and cut-offs, and the report shows how the lab reached its result.
Finger-prick or vein?
A vein sample is needed, taken into a clotting tube that must be filled to an exact level and processed promptly. Blood from a finger prick starts to clot as it is collected, so it cannot be used.
Anticoagulant medicines, including warfarin, heparin and the newer anticoagulant tablets, can interfere with the result.