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Test Code BLOD0661 Factor VIII (8) Assay

Useful For

  • Diagnosing hemophilia A
  • Diagnosing von Willebrand disease when measured with the von Willebrand factor (VWF) antigen and VWF activity
  • Diagnosing acquired deficiency states
  • Investigation of prolonged activated partial thromboplastin time


Clot Detection

Performing Laboratory

Bozeman Health Laboratory Services

Specimen Requirements

Specimen must arrive and be tested within 4 hours of draw.

Specimen Type: Whole blood
Container/Tube: Blue top (3.2% sodium citrate)

Specimen Volume: Full tube

Collection Instructions: Click here to link to a You Tube video tutorial

1. Immediately after draw, invert tubes several times to mix blood with additive.

2. Send specimen in original tube.

3. If there is a delay in transport of >4 hours, specimen must be double-centrifuged to prepare a platelet-free plasma specimen as follows:

a. Immediately centrifuge at 3,200 rpm for 15 minutes.

b. Carefully remove plasma from cells avoiding platelet/buffy coat, and transfer plasma into a plastic tube.

c. Centrifuge plastic tube at 3,200 rpm for 15 minutes.

d. Carefully remove top portion of plasma and transfer plasma into a plastic tube leaving approximately 250 mL in bottom to discard.

e. Double-centrifuged plasma should be aliquoted (0.5 mL-1 mL each) into clearly labeled plastic tubes. (Glass vial is not acceptable.)

Note: Number of tests ordered will determine number of aliquots needed, generally 1 aliquot per test.

f. Specimens should be frozen at <-40° C, if possible, and sent together in same container with at least 5 lbs of dry ice. Specimens must arrive in a frozen state.

Additional Information: Double-centrifuged specimen is critical for accurate results as platelet contamination may cause spurious results.

Specimen Transport Temperature

Ambient (whole blood) <4 hours/Frozen (plasma) >4 hours

Specimen Stability

Specmen Type Temperature Time
Whole Blood (unspun) Ambient 4 hours
Plasma Na Citrate (spun) Ambient 4 hours
Plasma Na Citrate (double spun) Frozen 14 days

Reference Values


Additional Information

  • Factor VIII, like von Willebrand Factor, is an acute phase reactant. Factor VIII levels rise during strenuous exercise, epinephrine or DDAVP administration, estrogen administration (birth control or hormone replacement therapy), during periods of acute stress, following surgery, and in most inflammatory conditions.
  • Factor VIII levels are elevated in carcinoma, leukemia, liver disease, renal disease, hemolytic anemia, diabetes mellitus, deep vein thrombosis, and myocardial infarction. In otherwise healthy individuals, levels are elevated at birth, increase during pregnancy, and also with age. Persistently elevated Factor VIII levels are thought to have, in part, a genetic basis.
  • Elevation of Factor VIII above 150% is seen in 11% of unselected individuals with venous thrombosis. Risk associated with elevated Factor VIII levels is graded and levels above 150% are associated with a 6X increase in thrombosis risk. Elevation of Factor VIII may shorten the aPTT and diminish sensitivity in testing for Factor Deficiencies, heparin therapy, or Lupus Anticoagulant.
  • Congenital deficiency of Factor VIII leads to Hemophilia A, an inherited sex-linked recessive disorder that causes severe bleeding. The severity of this bleeding disorder is inversely related to the Factor VIII concentration.  Hemophilia A patients are generally classified into three categories according to the Factor VIII Activity:

1 - Severe Hemophilia (<1%)
2 - Moderate Hemophilia (1% - 4%)
3 - Mild Hemophilia (5% - 25%)

  • Decreased Factor VIII levels may also be associated with von Willebrand Disease (VWD), or acquired secondarily due to other diseases such as liver diseases, or Disseminated Intravascular Coagulation (DIC).

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