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Test Code LAAPS3 LA/APS Functional Only (Intended for follow-up limited to functional abnormalities)

Specimen Type

Blood

Container

4 light blue top tubes, 3.2% sodium citrate

Preferred Volume

12 mL

Offsite Collection Instructions

Samples must be centrifuged at >1500 x g for 10 minutes at room temperature.
Carefully remove the plasma from the cells using a plastic transfer pipette avoiding the buffy coat.
Dispense the plasma into a plastic tube (glass is not acceptable) and centrifuge the plastic tube for a second centrifugation at >1500 x g for 10 minutes at room temperature.
Remove the top portion of the plasma being careful to leave a small amount of plasma at the bottom of the tube undisturbed (about 250mL). Then, aliquot the removed plasma into 4 plastic tubes containing minimum of 1.0 mL of specimen each.
The plasma samples must then be frozen at -20ºC.
Once solidly frozen they must be shipped on dry ice. Samples that have thawed in transit will be rejected.
Note: For clients who do not have access to dry ice do not freeze the specimen. Follow the centrifugation instructions or send whole blood sample. It now becomes vital that the specimen arrives in the lab within three hours of collection.

UCMC Collection Instructions

 
Specimens for this package may be collected and sent to the laboratory at any time

Availability

Functional lupus anticoagulant testing is performed 3 times a week, Monday- Friday 1st shift only.

Turnaround Time

3 days

STAT Availability

Not Available

Test Usage

The package includes functional lupus anticoagulant (LA) testing for detection of “antiphospholipid” antibodies.

Test Methodology

Clotting

Additional Information

Note: Each of the three functional LA testing systems now in use employ a heparin-neutralizing agent capable of neutralizing levels of heparin employed therapeutically in patients.  However, with the advent of direct thrombin inhibitors, these tests will no longer function properly to detect possible LA’s.  Accordingly, if the aPTT-LA screen is prolonged, a TT will be performed.  If this TT is prolonged, then a TT preceded by incubation of the plasma with heparinase will be performed to determine if heparin might be the cause of the prolongation. In contrast to plasma anticoagulated with unfractionated or low molecular weight heparin, plasma anticoagulated with direct thrombin inhibitors will not show a shortening of the TT following heparinase incubation.  Accordingly in such a situation, further LA functional testing will not be performed.

 

All 3.2% sodium citrate light blue top tubes require a ratio of 9 parts blood to 1 part anticoagulant (example: a 3.0 mL tube requires 2.7 mL blood added to 0.3 mL of anticoagulant).

CPT Code

85613; 85732; 85670; 85732; 85597; 85705

Test Includes

The package includes functional lupus anticoagulant (LA) testing by three independent systems—one based on a dilution of the Russell viper venom time (Dilute Russell Viper Venom Time, or “DRVVT”), one based on a dilution of the activated partial thromboplastin time (“PTT-LA”), and one based on a dilution of the prothrombin time (“dPT”). In each case a screening test is performed. If results in the screen are sufficiently prolonged, testing will proceed to a mixing study. If there is not sufficiently strong correction of the abnormality in the mixing phase, testing will then proceed to a confirmatory phase for that testing system. While the actual number of seconds of clotting times in the various phases of the specific testing systems necessarily varies as a function of reagent lot changes, the criterion for determination of normal vs abnormal with respect to detection of a LA remains constant: A 99th percentile upper limit for the normal reference population is determined for the confirmatory phase in each testing system at the time of lot changes, and is used as the basis for reporting of results in EPIC.

Reference Range

DRVVT Screen: <39.9 seconds
PTT-LA Screen: <41.8 seconds
dPT Screen: <49.3 seconds

Minimum Volume

12 mL

Fee Code

30585613, 30185732, 30085705

Synonyms

Lupus; LA; APS; LA/APS; APS/LA; Dilute Russell Viper Venom Screen (DRVVT); PTTLA; PTT with lupus sensitive reagent; Dilute Prothrombin Time (DPT)