Test Directory

This test screens for the factor V Leiden gene mutation and other causes of activated protein C resistance.

Specimen Type: Citrated Platelet-Poor Plasma

Collection Container: Light Blue Top (Sodium Citrate)

Desired Specimen Volume: 1 mL

1. Collect 2 light blue (sodium citrate) tubes via venipuncture.
2.  Evacuated collection tubes must be filled to completion to ensure a proper blood to anticoagulant ratio.
3.  The sample should be mixed immediately by gentle inversion at least six times to ensure adequate mixing of the anticoagulant with the blood.
4. A discard tube is not required prior to collection of coagulation samples, except when using a winged blood collection device (ie, "butterfly"), in which case a discard tube should be used.
5. When noncitrate tubes are collected for other tests, collect sterile and nonadditive (red-top) tubes prior to citrate (blue-top) tubes. Any tube containing an alternate anticoagulant should be collected after the blue-top tube. Gel-barrier tubes and serum tubes with clot initiators should also be collected after the citrate tubes.
6. If the patient's hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted

Platelet-Poor Plasma Processing Instructions

1. Citrated plasma samples should be collected by double centrifugation.
2. Perform platelet poor plasma processing procedure.
3. Transfer 1mL of platelet poor plasma to a LabCorp pp transpak frozen purple tube.

Do not draw from an arm with a heparin lock or heparinized catheter. Ideally, the patient should not be on anticoagulant therapy. Avoid warfarin (Coumadin®) therapy for two weeks prior to the test and heparin (direct Xa and thrombin inhibitor therapies) for about three days prior to testing.

Transport to the laboratory frozen. 

• Gross hemolysis
• Clotted specimen
• Frozen specimen thawed in transit
• Tubes <90% full
• Improper labeling
• Specimen collected in tube other than 3.2% citrate

See patient report.

This assay detects thrombotic risk factors other than factor V Leiden. This test should not be performed on individuals with extended baseline aPTT values due to the presence of lupus anticoagulants. This test should not be used for patients receiving thrombin inhibitors such as hirudin and argatroban. In some cases, this test will fail to distinguish individuals who are heterozygous for the factor V Leiden mutation from normals. Genetic testing may be required to distinguish between heterozygous and homozygous factor V Leiden mutation. Elevated factor VIII levels, as can be seen in acute phase reaction, can normalize the aPTT and effectively reduce the anticoagulant effect of aPC. Abnormal results can also be seen in pregnancy, especially during the third trimester, due to decreased levels of protein S and increased levels of factors V and VIII.

• APCR