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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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1- Sample collected in HMC facilities/others and transported to the lab within 1hour :
• Collect sample into light blue-top (sodium citrate).
• Tubes must be filled to within +/- 10% of their proper volume, to provide a 9:1 ratio of blood to citrate.
2- Samples collected in HMC facilities / others and which are expected not to reach the lab within 1hour:
• Centrifuge the whole blood and carefully remove the plasma by pipette not by decanting and send the plasma in a temperature-controlled environment (18-25ºC ) within one hour of centrifugation.
• If the transportation of the plasma can’t be within a maximum of 2hour , prepare platelet-poor plasma as follow:
A: Re-centrifuge plasma again.
B: Remove the top portion of plasma leaving approximately 250 mcL in the bottom to discard.
C: The double-centrifuged plasma should be aliquoted (0.5 to 1 mL per aliquot) into labeled plastic tubes. The number of tests ordered will determine the aliquots needed.
D: Freeze immediately at -20 ºC or below .
E: Specimens must arrive frozen.
3- Sample for Platelets function studies (Platelets function assay) , Citrated whole blood should reach HMC within a maximum of 1-2 hours of collection.
4- For heparin monitoring, follow the above mentioned steps. .
5- Consider patient HCT %. , if HCT >55%, the volume of anticoagulant in the tube must be adjusted by the referring lab, as per the below table shows the volume of citrate (µL) to be removed from common sizes of coagulation specimen tubes prior to specimen collection. After removal of the specified volume of citrate, enough blood is added to fill the tube to the ideal volume.
| Hematocrit % |
Volume to be removed, µL |
| 2.7 ml Tube |
1.0 ml Tube |
| 56 |
50 |
20 |
| 57 |
50 |
20 |
| 58 |
60 |
20 |
| 59 |
60 |
20 |
| 60 |
70 |
30 |
| 61 |
70 |
30 |
| 62 |
80 |
30 |
| 63 |
80 |
30 |
| 64 |
90 |
30 |
| 65 |
90 |
30 |
| 66 |
100 |
40 |
| 67 |
100 |
40 |
| 68 |
110 |
40 |
| 69 |
110 |
40 |
| 70 |
120 |
40 |
| 71 |
120 |
40 |
| 72 |
130 |
50 |
| 73 |
130 |
50 |
| 74 |
140 |
50 |
| 75 |
140 |
50 |
| 76 |
150 |
50 |
| 77 |
150 |
60 |
| 78 |
160 |
60 |
| 79 |
160 |
60 |
| 80 |
170 |
60 |
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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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