• Ideally the patient should not be on anticoagulant therapy
• Avoid heparin and direct Xa inhibitor therapies for about three days prior to testing

Lt blue Sodium citrate (NaCit) - 2.7mL

• Do not draw from an arm with a heparin lock or heparinized catheter.
• If the patient's hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted.
• Immediatley following collection, mix sample thoroughly by gentle inverting 8 - 10 times, to prevent clotting

1. Centrifuge for 10 minutes and carefully remove 2/3 of the plasma using a plastic transfer pipette, being careful not to disturb the cells.
2. Deliver to a plastic transport tube, cap, and recentifuge for 10 minutes.
3. Use a second plastic pipette to remove plasma, staying clear of the platelets at the bottom of the tube.
4. Transfer the plasma into a Screw-cap polypropylene frozen transport vial/tube - 4mL (LabCorp), labelled as Na cit plasma
5. Freeze immediately

Screw-cap polypropylene frozen transport vial/tube - 4mL (LabCorp)

Frozen (preferred) - 2 weeks

Freeze/thaw cycles: Stable x2

Ambient - 4 hours

Refrigerated - 4 hours

• Severe hemolysis
• Improper labeling
• Clotted specimen
• Specimen diluted with IV fluids
• Samples thawed in transit
• Improper sample type
• Sample out of stability

Factor VIII activity is determined by a two-stage chromogenic substrate assay where the amount of activated factor X generated is proportional to the amount of functional FVIII present in the test plasma in the presence of excess activated FIX. The amount of activated factor X generated is read with a chromogenic substrate and the activity is determined from a standard curve.

50 - 170%