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Factor VIII (von Willebrand Factor) Immunoassay, Qualitative

Published: August 9, 2026Updated: August 16, 2026

This test checks for the presence of Factor VIII, a protein that helps blood clot. It may be used to diagnose or monitor bleeding disorders or von Willebrand disease.

Quick summary

["This test helps determine if you have a clotting disorder by checking for Factor VIII protein levels."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
81712-2
Short code
F-actin Ab Ser Ql Line blot
Synonyms
F-actin Ab Ser Ql Line blot
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
line-blot
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why This Test Is Done

Your healthcare provider may order this test if you have symptoms of bleeding problems, such as excessive bruising, nosebleeds, or heavy menstrual periods. It may also be used to screen family members of those with known bleeding disorders or to monitor treatment for von Willebrand disease.

What to Expect Before the Test

No special preparation is needed. You may have a blood sample drawn from a vein in your arm. If you are on anticoagulant medication, discuss this with your provider before the test.

What the Test Results Mean

Results are qualitative (positive or negative) rather than quantitative. A positive result indicates the presence of Factor VIII protein, while a negative result suggests its absence or very low levels. This can help guide further testing or treatment plans.

Common Conditions Monitored

This test is primarily used to diagnose or confirm suspected bleeding disorders, including von Willebrand disease, hemophilia, or other inherited clotting factor deficiencies.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Factor VIII plays a critical role in blood clotting. Low levels can lead to excessive bleeding, while high levels may not be clinically significant in this context. Results help tailor treatment options, such as factor replacement therapy, for those with confirmed deficiencies.

Short name

Factor VIII Screening (Qualitative)

Frequently asked questions

What does a positive result mean?
A positive result means Factor VIII protein is detected in your blood, indicating normal or sufficient levels for clotting. This may help confirm a diagnosis of von Willebrand disease or rule out other bleeding disorders.
Can this test be used to diagnose hemophilia?
While this test checks for Factor VIII, it is not specific for hemophilia (which involves Factor VIII deficiency). Additional tests may be needed to confirm hemophilia or other clotting disorders.
Is fasting required for this test?
No fasting is required. Blood is typically drawn at any time of day, and it does not affect the test results.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy