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Test Code Billings Clinic: 2016 Factor VIII Assay, Plasma

Important Note

Call Hematology at (406)657-4062 if a presurgical STAT result is requested.

Performing Laboratory

Billings Clinic Laboratory: Coagulation

Useful For

  • Factor VIII assays are used for definitive identification of patients with deficient factor VIII activity (ie, patients with hemophilia A).
  • Patients with >30% factor activity usually exhibit few if any significant effects.



Specimen Requirements

Specimen Collection and Handling:

  • Draw blood in a light blue-top (3.2% sodium citrate) tube(s).
  • Immediately after draw, gently invert tube(s) at least 6 times to mix well.
  • Spin down, remove plasma, spin plasma again, and place 1 mL of citrate platelet-poor plasma in plastic vial.
  • Double-centrifuged specimens are critical for accurate results as platelet contamination may cause spurious results.
  • Glass vial is not acceptable.
  • Freeze specimen immediately at -20° C.


Specimen Transport:

  • Send specimen frozen.
  • DO NOT refrigerate specimen


Specimen Type Temperature Time
Plasma (citrated) Frozen (preferred) 2 weeks
  Ambient 3 hours

Reject Due To

  • Clotted Specimen
  • Specimen other than Citrated Plasma
  • Incorrect fill in specimen collection tube
  • Refrigerated specimen

Reference Values


Day(s) Test Set Up


Test Classification and CPT Coding

85240 - Clotting; factor VIII (AHG), 1-stage

LOINC Code Information

Reporting Name LOINC Code
Factor VIII Assay 3209-4


Specimen Requirements - Specimen Processing

Keep frozen at -70 until ready for testing.