Lupus Anticoagulant Screen (Blood)

Testing Laboratory

Department

Haematology

Delphic Registration Code (Alpha Code)

AAAA

Test Code (Numeric Code)

0000

Laboratory Handling

Phlebotomy

Tubes must be filled up to the "Fill Line"

Sample Stability

Testing should be done within 4 hours of sample collection or the plasma may be frozen for testing at a later date

Associated Tests

• Dilute Russel Viper Venom Time (Blood)

Synonyms

PTT-LA, Russel Viper Venom, RVV, Kaolin Clotting Time (Blood), Lupus Anticoagulant (Blood)

Turnaround Time

2 weeks

Assay performed every 7-10 days

Specimen Type

• Plasma

Specimen Requirements

Tube/Container Type:

Preferred

• Please refer to Additional Information below
• Citrate (Light Blue Cap)

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

• Please refer to Additional Information below

Additional Specimen Information

3 x 2.7 mL Citrate tubes (Light blue top)

Tubes must be filled up to the "Fill Line"

Limitations / Interference

LA frequently interfere with phospholipid-dependent coagulation tests, particularly the APTT as the reagent used at Middlemore is very sensitive to Lupus anticoagulant. Importantly, the clotting test abnormalities caused by LA are in vitro phenomena: the anti-phospholipid antibodies of the LA react with the phospholipid preparations used to initiate clotting reactions. In vivo, clotting factor activities are not diminished and, except in extremely rare cases where there are specific antibodies directed against clotting factor II (Prothrombin), there is no danger of a bleeding diathesis. A minority of patients with LA have a hypercoagulable state manifested by recurrent thrombosis, multiple spontaneous miscarriages or stroke.

Uncertainty of Measurement

APTT 6%; DRVV 5%

Additional Costing Information

For pricing inquiries, please contact us at 092760167

Most patients with LA do not have SLE and only 20-45% of patients with SLE develop LA.
Other clinical associations with antiphospholipid antibodies include; infections (viral e.g. HIV, varicella, hepatitis C); lymphoproliferative diseases (lymphoma, paraproteinaemias); drug exposure (Phenothiazines, Procainamide, Phenytoin, Quinidine, Hydralizine) and other miscellaneous disorders including autoimmune thrombocytopenia and Autoimmune haemolytic anaemia.

The initial screening tests for Lupus anticoagulant are PR and APTT plus mixing studies if either PR or APTT are abnormal.
Dilute Russells Viper Venom (DRVVT) will also be performed.

In the DRVVT, Russells viper venom activates factor X which in turn activates Prothrombin in the presence of calcium ions, factor V and phospholipid, leading to the formation of a fibrin clot. If the venom is diluted to give a suitable clotting time and the phospholipid reagent is diluted so that its concentration becomes rate limiting, any inhibition of the coagulant active phospholipid by LA results in a prolonged DRVVT. If the DRVVT is abnormal the lab will perform a DRVVT 1+1, where the patient's plasma is mixed with an equal amount of normal plasma. If the abnormality is due to LA, the 1+1 result will also be abnormal.

The KCT is no longer recommended as a routine screening test for LA. (Reference - Update of the guidelines for lupus anticoagulant detection, Journal of Thrombosis and Haemostasis, 7:1737-1740) The KCT will only be performed if LA is suspected and the DRVVT is negative.

Contact Information

Contact Information