Specimen Requirements

Citrated whole blood, citrated plasma and EDTA whole blood are ALL required for this test.

APTT, Factor VIII Assay, PT, and Ristocetin Cofactor

• Riverside Inpatient or Riverside Campus draw sites:

Testing must be performed within 4 hours of draw if submitting unprocessed whole blood.

Draw 6 full, light blue-top (citrate) tubes; and send citrated whole blood. Invert several times to mix blood. Do not centrifuge. Forward unprocessed whole blood promptly at ambient temperature only. Do not refrigerate. Specimen cannot be frozen.

• Outpatient/Outreach Clients

Plasma-Frozen

Draw 10 full, light blue-top (citrate) tubes, aliquot plasma, double spin and aliquot again. Send plasma.

• Note:  Gross hemolysis, lipemia, or icteric specimen may affect results.
• Label each specimen appropriately (citrated whole blood for APTT, Factor VIII activity, PFA, PT, and ristocetin).

Platelet Count and Platelet Morphology

• Draw a full, lavender-top (EDTA) tube; and send EDTA whole blood. Invert several times to mix blood. Do not centrifuge.
• Forward unprocessed whole blood promptly at ambient temperature if received within 24 hours. Specimens stored refrigerated 2-8 degrees are acceptable for up to 48 hours. Specimens canot be frozen.

Note:  Label specimen appropriately (EDTA whole blood for platelet count and morphology).

von Willebrand Factor Antigen

• Collection Container/Tube: Light-blue top (3.2% sodium citrate)
• Collection Instructions:
  • Centrifuge, transfer all plasma into a plastic vial, and centrifuge plasma again.
  • Aliquot plasma into a plastic vial, leaving 0.25 mL in the bottom of centrifuged vial.
  • Freeze plasma immediately (no longer than 4 hours after collection) at -20° C or, ideally, less than or equal to -40° C.
• Additional Information:
  • Double-centrifuged specimen is critical for accurate results as platelet contamination may cause spurious results.
  • Each coagulation assay requested should have its own vial.

PFA

• Specimen must arrive in laboratory within 3 hours of draw. If specimen is transported by courier, please inform courier of PFA specimen which needs to be taken to testing area within 3 hours from draw time.

• Draw 2 full, light blue-top (citrate) tubes; and send citrated whole blood. Invert several times to mix blood. Do not centrifuge. Forward unprocessed whole blood promptly at ambient temperature only. Do not refrigerate. Specimen cannot be frozen.
• Note: 
  • Certain fatty acids and lipids found in various human diets are widely known to inhibit platelet function. Physicians may wish to advise patients to refrain from fatty foods prior to testing.
  • Presence of hemolysis may interfere with test results. Platelet inhibiting agents such as aspirin and anti-glycoprotein IIb/IIIa antagonists directly affect platelet function. Avoid aspirin and other antiplatelet drugs for 7 to 10 days prior to test.