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Factor VIII Activity

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Report in 48Hrs

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No Fasting Required

Details

Factor VIII Activity — a crucial test in evaluating clotting function and bleeding disorders

₹3,149₹3,850

18% OFF

Factor VIII Activity Test Information Guide

  • Why is it done?
    • Measures the functional activity level of clotting factor VIII, a critical protein in the blood coagulation cascade responsible for normal blood clot formation
    • Diagnose hemophilia A, the most common inherited bleeding disorder caused by deficiency or dysfunction of factor VIII
    • Evaluate unexplained bleeding or prolonged bleeding time, including easy bruising, joint hemorrhages, or excessive bleeding after surgery or trauma
    • Monitor patients with known hemophilia A during treatment with factor VIII replacement therapy or inhibitor bypassing agents
    • Assess bleeding risk prior to surgical procedures or invasive interventions in patients with personal or family history of bleeding disorders
    • Investigate abnormal activated partial thromboplastin time (aPTT) results in routine coagulation screening
    • Screen female carriers of hemophilia A, as some may have clinical manifestations due to skewed X-inactivation patterns
  • Normal Range
    • Normal Range: 50-150% (or 0.5-1.5 IU/mL) Typical reference range is 50-150% of normal activity, though this may vary by laboratory
    • Unit of Measurement: Percentage (%) or International Units per milliliter (IU/mL)
    • Normal Result: Factor VIII activity levels between 50-150% indicate adequate clotting factor function and normal coagulation capability
    • Low Result: Less than 50% indicates reduced factor VIII activity, which may cause impaired blood clotting and increased bleeding risk
    • High Result: Greater than 150% may occur after factor VIII replacement therapy, acute illness, stress, or certain medications, though rarely causes clinical problems
  • Interpretation
    • Factor VIII <1% (Severe Hemophilia A): Indicates severe deficiency with high risk of spontaneous bleeding into joints (hemarthroses), muscles, and internal organs. Patients require prophylactic factor VIII replacement therapy.
    • Factor VIII 1-5% (Moderate Hemophilia A): Moderate deficiency with bleeding occurring after trauma or surgery. May have occasional spontaneous bleeding episodes. Requires treatment on-demand or prophylactic therapy depending on clinical presentation.
    • Factor VIII 5-40% (Mild Hemophilia A): Mild deficiency with bleeding primarily after significant trauma or surgery. Spontaneous bleeding is rare. Patients often experience prolonged bleeding after dental procedures or injuries.
    • Factor VIII 40-50% (Borderline Low): Mildly reduced levels that may warrant clinical follow-up. Some individuals may experience excessive bleeding with surgery or trauma, while others remain asymptomatic.
    • Factors Affecting Results: Recent factor VIII replacement therapy, acute illness or stress, estrogen use (contraceptives, hormone replacement therapy), von Willebrand disease, disseminated intravascular coagulation, liver disease, vitamin K deficiency, certain medications (aspirin, warfarin), and improper blood sample collection or processing
    • Clinical Significance of Result Patterns: Factor VIII activity typically correlates with bleeding risk; lower levels generally indicate greater hemophilia severity. Serial measurements help monitor treatment efficacy. Persistently low levels in previously adequate patients may indicate development of factor VIII inhibitors (neutralizing antibodies), necessitating specialized testing and alternative treatment strategies.
  • Associated Organs
    • Primary Organ System: Hematopoietic system and blood vessels. Factor VIII is produced by endothelial cells and megakaryocytes, functioning as a vital component of the intrinsic coagulation pathway.
    • Hemophilia A: X-linked recessive genetic disorder causing deficient or dysfunctional factor VIII, affecting primarily males and carrier females
    • Von Willebrand Disease: Deficiency of von Willebrand factor can lead to secondary reduction in factor VIII levels, as von Willebrand factor stabilizes and carries factor VIII in circulation
    • Acquired Factor VIII Deficiency Conditions: Liver disease, severe malnutrition, vitamin K deficiency, disseminated intravascular coagulation, systemic lupus erythematosus, multiple myeloma, and lymphoproliferative disorders
    • Complications from Low Factor VIII Activity: Hemarthroses (joint bleeding) leading to chronic arthropathy, intramuscular hematomas, gastrointestinal bleeding, hematuria, intracranial hemorrhage (potentially fatal), retrobulbar hemorrhage, and pseudotumor formation (large hematomas that can compress surrounding tissues)
    • Affected Target Sites: Joints (knees, ankles, elbows), muscles, mucous membranes, gastrointestinal tract, urinary tract, brain, and eyes. Repeated bleeding in joints causes hemophilic arthropathy with pain, swelling, and progressive joint destruction.
  • Follow-up Tests
    • Factor VIII Inhibitor Testing (Bethesda Assay): Recommended when factor VIII levels fail to increase appropriately after factor VIII replacement therapy, as inhibitors are neutralizing antibodies that block factor VIII activity
    • Activated Partial Thromboplastin Time (aPTT): Initial screening test that typically shows prolongation with low factor VIII levels; helps determine if factor VIII activity testing is warranted
    • Von Willebrand Factor Assays: Test von Willebrand factor antigen and activity if low factor VIII occurs without hemophilia A, as von Willebrand disease is another common cause of low factor VIII
    • Other Coagulation Studies: Prothrombin time (PT), fibrinogen level, and platelet count to evaluate overall hemostatic function and identify other coagulation abnormalities
    • Genetic Testing for Factor VIII Gene Mutations: Identifies specific factor VIII gene defects, helpful for family counseling, carrier detection, and understanding disease severity patterns
    • Liver Function Tests (LFTs): Assesses liver function since acquired factor VIII deficiency can occur with liver disease, and liver disease screening is important for patients receiving blood products
    • Mixing Study (1:1 aPTT Mix): Distinguishes between factor deficiency and inhibitor presence; prolonged aPTT that corrects with mixing suggests factor deficiency, while uncorrected aPTT suggests inhibitor
    • Monitoring Frequency for Established Hemophilia A: Regular factor VIII levels prior to major surgery or invasive procedures; periodic monitoring (every 3-6 months) in patients on prophylactic therapy; more frequent testing if bleeding episodes occur; annual inhibitor screening recommended in newly diagnosed patients during first 50 exposure days to factor VIII products
  • Fasting Required?
    • Fasting Required: No - Factor VIII activity testing does not require fasting. Patients may eat and drink normally before the test.
    • Patient Preparation Instructions: Arrive well-hydrated to facilitate blood draw; inform phlebotomist of any recent factor VIII replacement therapy received within the past 24 hours, as this affects results interpretation
    • Medications to Avoid or Report: Inform healthcare provider of all current medications, particularly antiplatelet agents (aspirin, NSAIDs), anticoagulants (warfarin, direct oral anticoagulants), corticosteroids, estrogens (oral contraceptives, hormone replacement therapy), and any factor VIII replacement products. Do not discontinue prescribed medications unless instructed by physician. Recent desmopressin (DDAVP) use should be reported.
    • Specimen Collection Considerations: Blood sample is collected in a citrated tube (usually 3.2% sodium citrate). Proper tube fill volume is critical; too little or too much anticoagulant invalidates results. The sample must be mixed gently to ensure adequate anticoagulation. Processing should begin promptly (within 1-2 hours) to maintain factor VIII stability.
    • Optimal Timing: Baseline factor VIII testing is best performed at least 3 days after any factor VIII replacement therapy to assess intrinsic factor VIII production. For monitoring therapy effectiveness, obtain "peak" levels 20-30 minutes after intravenous factor VIII infusion or "trough" levels just before the next scheduled dose.
    • Additional Requirements: No special skin preparation needed beyond standard blood draw protocol. Avoid strenuous activity or heavy lifting for 24 hours after blood draw to prevent hematoma formation. Patients with a history of difficult venipuncture should inform the phlebotomist in advance. Maintain stable body temperature (avoid overheating) before testing as factor VIII activity can increase with elevated body temperature.

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