- Avoid use of pneumatic tubes for transporting specimens.
- Please arrange for delivery by an Orderly if possible.
- Tube must be adequately filled.
| Tests | Normal Range | Uncertainty of measurement |
|---|---|---|
|
PTT-LA (20% Index) |
0.9 - 1.1 | 4% |
| PTT-LA | 34 - 51 | 4% |
| RVV ratio | 0.8 - 1.2 | 6% |
| RVV index | 0.8 - 1.2 | 6% |
Tests performed each week, and the findings will be commented on in the report.
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 the 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 antiphospholipid syndrome requires the same abnormal laboratory test/s (lupus anticoagulant, anticardiolipin antibodies and anti- beta2 antiglycoprotein-1) remains positive at least three months apart.
- To determine whether the lupus anticoagulant is temporary (transient) or persistent
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 or direct anti-Xa drugs including Dabigatran and Rivaroxaban will have false-positive results for lupus anticoagulant. Warfarin anticoagulant therapy may also cause false test results if levels of coagulation factor II, VII, IX and X are significantly decreased. If possible, lupus anticoagulant testing should be done prior to the start of anticoagulation therapy.
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.
For further information contact the Haematology laboratory (Ext 22067) or:
| Dr Nicola Eaddy | Ext 22071 | |
| Dr Peter Bradbeer | Ext 22062 | |
| Dr Anna Ruskova | Ext 22137 |
If the specimen is collected from outside Auckland Hospital, please filter the plasma through a 0.2 um Minisart Single use filter unit.
Please contact Lablink to arrange for the supply of the filter. This is the preferred specimen for lupus anticoagulant testing.
If the filter unit is not available the specimen should be double-spun to ensure platelet depletion.
Plasma should be sent frozen.
State on the request form whether the plasma is filtered or double-spun so the correct reference values a can be applied