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Lab Dept:
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Coagulation
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Test Name:
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LUPUS INHIBITOR DETECTION
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General Information
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Lab Order Codes:
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LUPI, LIM
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Synonyms:
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Lupus Anticoagulant, Lupus Inhibitor
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CPT Codes:
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85612 – Dilute Russell’s Viper Venom Test (DRVVT)
85613 – (DRVVT MIX), LIM
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Test Includes:
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LA1 Screening Test, LA2 Confirmatory test, LA1/LA2 Ratio
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Logistics
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Test Indications:
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Ordered as a result of an elevated PTT that does not correct with the addition of Pooled Normal Plasma. Ordered separately to monitor the presence of a persistent Lupus Inhibitor.
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Lab Testing Sections:
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Coagulation (Minneapolis Campus)
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Phone Numbers:
Minneapolis:
Saint Paul:
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612-813-6280
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651-220-6550
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Test Availability:
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Daily, 24 hours
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Turnaround Time:
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2 – 3 days (Performed once daily, Monday - Friday)
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Special Instructions:
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Deliver immediately to the laboratory at room temperature. Indicate when specimen is drawn from a line or a heparin lock.
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Specimen
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Specimen Type:
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Whole blood
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Container:
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Light Blue (Buffered Na Citrate 3.2%) top tubes
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Draw Volume:
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5.4 mL in 2 – 2.7 mL tubes (Minimum: 2.7 mL)
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Processed Volume:
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1.8 mL (Minimum 0.9 mL) plasma
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Collection:
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A clean venipuncture is essential.
If the patient’s hematocrit is >55%, call the laboratory for a special tube. Fill tube completely.
Mix thoroughly by gentle inversion.
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Special Processing:
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Lab Staff: All testing will be performed in Minneapolis.
St Paul Lab: Send whole blood specimens to Minneapolis Lab for processing via courier. Must be processed within 4 hours of collection. Contact Minneapolis Lab prior to sending.
Minneapolis Lab: Centrifuge specimen, remove plasma sample taking care not to disturb buffy coat. Perform a second spin after removing plasma from the original collection containers. Aliquot into two screw-top plastic vials (Minimum: 0.5 mL in each tube).Store frozen at –70degrees C.
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Patient Preparation:
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None
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Sample Rejection:
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Improper tube, Clotted sample, Underfilled tube, Overfilled tube, Mislabeled or unlabeled specimens.
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Interpretive
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Reference Range:
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Ranges apply to all ages:
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LA Screening Test (LA1)
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<45 seconds
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LA Confirmatory Test (LA2)
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<40 seconds
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LA1/LA2 ratio
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<1.40
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Critical Values:
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N/A
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Limitations:
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If heparin contamination is suspected the heparin removal procedure should be performed.
Icteric, lipemic and hemolyzed samples may interfere with the detection of the clot on some photoelectric instruments.
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Methodology:
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LA1 Screening Reagent: Russell’s Viper Venom initiates clotting by directly activating factor X. LA antibodies prolong the LA1 Screening Reagent clotting time. The LA1 Screening Reagent is more specific for LA than PTT’s because deficiencies of the extrinsic pathway (factor VII), contact factor abnormalities (factors XI, XII) as well as hemophilic factors (factors VII,IX) are bypassed in this reaction.
LA2 Confirmation Reagent: Confirmation Reagent is similar to LA1 Screening Reagent but contains a high phospholipid concentration. The extra phospholipid counteracts the LA antibody and largely corrects the clot time.
LA1/LA2 ratio: The higher the ratio the stronger the inhibitor.
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References:
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An Algorithmic Approach to Hemostasis Testing (2008), Kandice Kottke- Marchant Chapter 22, pp. 296-303
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BCS-XP System Instruction Manual (2006), 1 000 767.0506 Manual Version 1.0 Siemens; Marburg, Germany. Automated Protocol for Dade Behring Analyzers
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LA1 Screening Reagent/LA2 Confirmation Reagent product insert OQGP G15 U1131
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Test kit Code No. OQGP (LA1)
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Test kit Code No. OQGR (LA2)
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Control, Lupus Anticoagulant Low, OQWE11
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Control, Lupus Anticoagulant High, OQWD11
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Control Plasma N (2008 July), ORKE T45 U1135, Siemens; Marburg, Germany
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The Clotting Times, Vol. 4, Issue 4, Jan. 2005: Functional Laboratory Testing for Lupus Anticoagulant
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Updates:
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5/7/2012: Draw volume changed, previously listed as 8.1 mL (Min: 5.4 mL).
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