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Vw (Von Willebrand) Factor Antigen
Blood
Report in 192Hrs
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No Fasting Required
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Von Willebrand factor level.
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Von Willebrand Factor Antigen Test - Comprehensive Medical Guide
- Why is it done?
- Measures the quantity of von Willebrand factor protein in the blood, which is essential for blood clotting and platelet adhesion
- Diagnose von Willebrand Disease (VWD) - a bleeding disorder affecting blood clotting ability
- Evaluate unexplained bleeding or bruising, nosebleeds, heavy menstrual bleeding, or prolonged bleeding after surgery or dental procedures
- Assess family history of bleeding disorders before surgery or invasive procedures
- Monitor treatment effectiveness in patients with diagnosed von Willebrand Disease
- Typically performed as part of a coagulation profile when bleeding disorders are suspected
- Normal Range
- Reference Range: 50-160% or 0.50-1.60 IU/mL (International Units per milliliter)
- Normal Results: Values within 50-160% indicate adequate von Willebrand factor levels for normal blood clotting function
- Low Results: Below 50% may indicate von Willebrand Disease or other bleeding disorders
- High Results: Above 160% may occur with inflammation, stress, estrogen therapy, or blood type O (normal variant)
- Units of Measurement: Percentage (%) or International Units per milliliter (IU/mL)
- Interpretation Note: Normal VWF:Ag does not exclude von Willebrand Disease; must be interpreted with VWF:RCo (ristocetin cofactor activity) and Factor VIII levels
- Interpretation
- Mildly Reduced (30-50%): May indicate Type 1 or Type 2 von Willebrand Disease; borderline results require repeat testing and clinical evaluation
- Moderately Reduced (20-30%): Consistent with Type 2 von Willebrand Disease; significant bleeding risk
- Severely Reduced (<20%): Suggests Type 3 von Willebrand Disease (complete deficiency); requires immediate treatment planning
- Elevated Levels: May occur temporarily during acute stress, infection, inflammation, pregnancy, estrogen use, or blood type O (lower normal baseline); typically not clinically significant
- Factors Affecting Results: Blood type (Type O individuals have 25% lower levels), stress, physical activity, time of testing (seasonal variations), menstrual cycle, oral contraceptives, estrogen therapy, thyroid disorders, and systemic conditions
- Clinical Significance: Results must be correlated with clinical symptoms, family history, and other coagulation tests; VWF:Ag alone cannot diagnose von Willebrand Disease without additional testing (VWF:RCo, Factor VIII, bleeding time studies)
- Associated Organs
- Primary Organ System: Hematologic (Blood) and Hemostatic System - von Willebrand factor is produced by endothelial cells and megakaryocytes
- Von Willebrand Disease Types: Type 1 (partial quantitative deficiency), Type 2 (qualitative or partial quantitative deficiency with variants), Type 3 (complete deficiency)
- Associated Conditions with Low VWF:Ag: Von Willebrand Disease, Hemophilia A (Factor VIII deficiency), hypothyroidism, uremia, liver disease, disseminated intravascular coagulation (DIC)
- Associated Conditions with Elevated VWF:Ag: Acute infection, inflammation, thrombotic thrombocytopenic purpura (TTP), hemolytic uremic syndrome (HUS), atherosclerosis, diabetes mellitus, systemic vasculitis
- Complications of Abnormal Results: Low levels: excessive bleeding, hemorrhage, mucosal bleeding, joint bleeds (hemarthrosis), intracranial hemorrhage; High levels: increased thrombotic risk in specific conditions
- Organs Affected by Severe Deficiency: Brain (hemorrhagic stroke risk), GI tract (gastrointestinal bleeding), urinary system (hematuria), reproductive organs (menorrhagia, hematospermia)
- Follow-up Tests
- If VWF:Ag is Abnormal: VWF:RCo (von Willebrand Factor: Ristocetin Cofactor Activity) - measures functional activity
- Factor VIII activity level - von Willebrand factor stabilizes Factor VIII
- Prothrombin time (PT) - assesses extrinsic coagulation pathway
- Activated partial thromboplastin time (aPTT) - screens for intrinsic coagulation defects
- Bleeding time or PFA-100 (Platelet Function Assay) - evaluates platelet function
- Platelet count - assesses platelet availability for clotting
- Additional Confirmatory Tests: VWF:RCo to VWF:Ag ratio, VWF:GPM (glycoprotein M binding), genetic testing for VWD mutations if diagnosis suspected
- Monitoring in Diagnosed Patients: Repeat VWF:Ag testing 3-6 months apart (levels can vary significantly), before surgical procedures, annual assessment for disease progression
- Treatment Monitoring Tests: VWF:Ag and Factor VIII levels after desmopressin (DDAVP) therapy to assess response to treatment
- Fasting Required?
- Fasting Requirement: No - fasting is not required for this test
- Patient Preparation Instructions: Maintain normal diet and hydration; no dietary restrictions necessary
- Activity Before Test: Avoid strenuous exercise for 24 hours before testing (physical stress can elevate VWF levels); maintain normal daily activities
- Medications to Avoid or Note: Aspirin and NSAIDs - may affect platelet function (discontinue 3-5 days before if possible); inform physician of all medications, particularly anticoagulants, estrogens, and desmopressin; do NOT discontinue prescribed anticoagulants without medical approval
- Important Timing Considerations: Avoid testing during acute illness, stress, or within 3 weeks after surgery as these conditions elevate VWF levels; schedule test when patient is in stable health; women should ideally avoid testing during menstruation (hormonal fluctuations affect levels)
- Sample Collection: Blood draw via venipuncture into citrated collection tube; proper technique essential as rough handling or improper collection may affect test results
- Pre-Test Hydration: Maintain normal hydration but avoid excessive fluid intake immediately before testing
How our test process works!
