What is lupus?
It is a chronic, inflammatory autoimmune condition in which the immune system starts producing inappropriate immune response against its own tissues. It affects skin, joints, blood vessels & internal organs.
What is the Lupus Anticoagulant Lab test?
Lupus anticoagulants (LA) are the autoantibodies that are produced because of immune response against the body's own cells. These autoantibodies attack phospholipids & proteins associated with phospholipids. They also hinder the clotting process of blood and show increased risk of developing inappropriate blood clots. Hence, this test is used to detect the presence of LA in blood. No single test is used for detection of lupus anticoagulant. It cannot be measured directly and requires a panel of sequential lab tests.
Why is lupus anticoagulant lab test done?
The test purpose is to detect lupus anticoagulants in blood. Hence, this LA testing helps determine:
- Cause of unexplained blood clot in vein or artery
- Recurrent miscarriages in a female
- Cause of unexplained prolonged PTT test (partial thromboplastin time).
- With other tests for diagnosis of APS (antiphospholipid syndrome)
- With other tests for diagnosis of thrombophilia (excessive clotting disorder)
- Whether LA is permanent or temporary.
The series of tests that are performed for LA include:
- The LA-Screen test for detection includes DRVVT (dilute Russell viper venom test) & LA-sensitive PTT.
- Follow-up tests to confirm presence of LA includes Mixing study & LA-Confirm.
- Which test is recommended for determining lupus anticoagulants?
Two tests DRVVT & PPT-LA are used to detect lupus anticoagulants (LA-screen).
- What do positive lupus anticoagulant tests mean?
As previously perceived, positive LA doesn't indicate that person has lupus or that blood is prevented from clotting. It rather means that blood in the body is clotting too easily.
- What is the normal lupus anticoagulant range?
Its normal values range from 20 to 39 GPL or MPL units.
- Why is repeated testing required for lupus anticoagulants?
These autoantibodies appear with infection & go away once infection resolves, hence, repeated testing over a period is required for confirmation.
- Is LA presence a serious condition?
Its presence in an individual is associated with predisposition towards blood clots. And blood clots anywhere in body leads to serious complications.
INTERPRETATION OF THE RESULTS:
As mentioned above a series of tests are performed for confirmed detection of lupus antibodies. The results of various tests are interpreted as follows:
- PT: 28.60 to 41.10 seconds
- PTT-LA: 31.40 to 43.40 seconds
- DRVVT: No LA present
- Step 1 "PTT-LA and/or DRVVT":
- NORMAL = no further testing required
- PROLONGED = inhibitor maybe present, so perform step 2
- Step 2 "Mixing Study":
- NORMAL = step 1 abnormal due to coagulation factor deficiency
- PROLONGED = lupus anticoagulants maybe present, so perform step 3
- Step 3 "Confirmation (correction or neutralization test)":
- POSITIVE HIGH RATIO = LA present
- NEGATIVE LOW RATIO = other than LA, specific inhibitors are present.
Lupus Anticoaulant test helps in investigating the cause of a blood clot, evaluate prolonged PTT test, cause of recurrent miscarriages, or to evaluate antiphospholipid syndrome. However, this test doesn't diagnose SLE (commonly known lupus condition).