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Test ID: Lupus Anticoagulant
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Lupus Anticoagulant
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Useful For
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To detect antibodies against Phospholipids and as Screening for thrombophilia
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Method name and description
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Turbidimetric.
Dilute Russell’s Viper Venom Test (DRVVT) for detection of Lupus Anticoagulants. Test is performed using Sysmex CS5100 analyzer. Russell’s viper venom present in LA1 Screening Reagent initiates plasma clotting by directly activating factor X. LA antibodies prolong the LA1 Screening Reagent clotting time. LA2 Confirmation Reagent is like LA1 Screening Reagent but contains a high phospholipid concentration. The extra-phospholipid counteracts the LA antibody and largely corrects the clot time.
DRVV test “bypasses” factor VII of the extrinsic pathway, the contact and antihemophilic factors of the intrinsic pathway. Therefore, LA1 Screening Reagent is more specific for LA than APTT as it is not affected by contact factor abnormalities or by factor VIII deficiencies or antibodies. Mixing normal plasma with test plasma replenishes any factor deficient in the test plasma. Heparin levels up to 1U/mL have no effect due to the presence of neutralizing agent in both LA 1 Screening Reagent and LA 2 Confirmation Reagent.
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Clinical information
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LAs are autoantibodies against negatively charged phospholipids or complexes of
phospholipids with either beta-2-glycoprotein 1 or clotting factors such as prothrombin. They occur in various clinical conditions, especially autoimmune diseases such systemic lupus erythematosus and collagen vascular disease. It can occur in response to medications or infections and in individuals with no obvious underlying disease. It is a significant risk factor in patients with otherwise unexplained thrombosis and are often present in women who have recurrent fetal loss. LAC has been associated as well with thrombocytopenia or factor II deficiency with consequent risk for bleeding.
A single positive test should be repeated after 12 weeks to exclude transient occurrence which is seen in the course of many illnesses or medication.
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Specimen type / Specimen volume / Specimen container
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Plasma Na Cit. Platelet-poor plasma.
The specimen must be double-centrifuged.
Specimen Volume: 2.7 ml.
Container/Tube: Light-blue top (citrate)
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Collection instructions / Special Precautions / Timing of collection
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- Samples collected in HMC facilities MUST reach the coagulation laboratory within 1 hour of collection.
- Samples collected in non-HMC facilities / external clients: MUST reach coagulation laboratory within 1 hour of collection, if not applicable, centrifuge the whole blood and carefully remove the plasma (by pipette not by decanting) and send it in a temperature-controlled environment (18- 25 ºC) within 2 hours of centrifugation. If the transportation of the plasma can’t be within a maximum of 2 hours, prepare platelet-poor plasma as follows:
- Re-centrifuge the plasma again.
- Remove the top portion of plasma leaving approximately 250 ul in the bottom to discard.
- The double-centrifuged plasma should be aliquoted into labeled plastic tubes.
- Freeze immediately at -20 ºC or below
- Specimens must arrive frozen.
- If patient HCT is >55%, test will not be processed. The ordering Physician will be contacted to reorder the test and call the patient to go to Phlebotomy for recollection. Instruct the patient to inform the phlebotomy about his high HCT% , the phlebotomy will contact the lab to request a coagulation tube after adjusting amount of anticoagulant.
Note:
Collection of blood for coagulation testing through intravenous lines that have been previously flushed with heparin should be avoided, if possible. If the blood must be drawn through an indwelling catheter, possible heparin contamination and specimen dilution must be considered. When obtaining specimens from indwelling lines that may contain heparin, the line should be flushed with 5 mL of saline, and the first 5 mL of blood or 6-times the line volume (dead space volume of the catheter) be drawn off and not used for coagulation testing. For those specimens collected from a normal saline lock (capped off venous port) twice the dead space volume of the catheter and extension set should be discarded.
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Relevant clinical information to be provided
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LA testing is not recommended in patients on DOACs because of false positive results. The test should be preceded by stopping DOACs the day before and on the day of testing. Patient/family history of bleeding disorder. History of anticoagulant therapy. History of chronic diseases
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Storage and transport instructions
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Specimen Rejection Criteria
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Specimens with no label or missing required identification
Broken, leaking or contaminated specimen
Clotted samples
Under-filled or overfilled sample tubes.
Wrong sample container sample received
Improper specimen transport temperature (e.g. like specimens which are needed to be sent on ice)
Old specimen (test-dependent)
Grossly Hemolyzed sample (test-dependent)
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Biological reference intervals and clinical decision values
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LA result reported in seconds and/or ratio.
Reference range:
LA1 (LAS = 30.4- 45.3 sec)
LA2 (LAC = 27.7 – 33.5 sec)
Ratio = (1.01 - 1.41)
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Factors affecting test performance and result interpretation
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No interference up to:
Triglycerides 243 mg/dl.
Hemoglobin 40 mg/l.
Bilirubin 6 mg/dl.
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Turnaround time / Days and times test performed / Specimen retention time
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3 working days / Daily / NA.
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