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

Specimen Type

Plasma

Container/Tube

4 light blue top tubes, 3.2% sodium citrate

Offsite Collection Instructions

Whole blood sample must arrive in the laboratory within
three hours of specimen collection.

 

If transport time exceeds three hours, follow centrifugation
instructions:

  • Samples must be centrifuged at >2500 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 >2500 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 a minimum of 1.0 mL of specimen in each tube.
  • The plasma samples must then be frozen at -20 C.
  • Once solidly frozen they must be shipped on dry ice. Frozen
    plasma 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 and
send fresh plasma or send whole blood sample. It now becomes
vital that the specimen arrives in the lab within three hours of
collection.

Turnaround Time

3 days

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.

Preferred Volume

8 mL in 4 aliquots, 2 mL each

UCMC Collection Instructions


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

Test Usage

The package includes functional lupus anticoagulant (LA)
testing only for detection of antiphospholipid antibodies. Designed for
follow up testing for patients with LA without antiphospholipid
antibodies

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 LAs.
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).

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)

STAT Turnaround Time

n/a

Specimen Minimum Volume

5 mL

DAY(S) AND TIME(S) PERFORMED

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

STAT DAY(S) AND TIME(S) PERFORMED

Not Available

CPT

85613; 85732; 85670; 85732; 85597; 85705

Method Name

Clotting

Reference Values

DRVVT Screen: <41.0 seconds
PTT-LA Screen: <40.6 seconds
dPT Screen: <46.9 seconds

Reject Due To

Specimens that have wrong ratio of blood to anticoagulant
(fill volume) clotted or grossly hemolyzed.