Hemophilia – Factor VIII or IX Deficiency

Hemophilia A and hemophilia B are bleeding disorders caused by genetic variants in the F8 or F9 gene that result in deficiencies of factor VIII (FVIII) or factor IX (FIX), respectively. These disorders are clinically indistinguishable and present with bleeding symptoms ranging from mild to severe, depending on the underlying defect.

  • Diagnosis
  • Monitoring
  • Background
  • Lab Tests
  • References
  • Related Topics

Indications for Testing

  • Spontaneous or prolonged bleeding suggestive of coagulation disorder
  • Family history of hemophilia
  • Acute or recent onset bleeding accompanied by prolonged partial thromboplastin time (PTT)

Initial Laboratory Testing for Coagulation Disorders

  • CBC with platelet count – normal in hemophilia A and B
  • Prothrombin time (PT) – normal in hemophilia A and B
    • PTT – prolonged in moderate and severe hemophilia
    • Often normal in mild cases or in female carriers
    • PTT that corrects with mixing study suggests factor deficiency
    • PTT that does not correct with mixing study suggests an inhibitor
  • Mixing study – incubated mixing studies are often necessary to identify presence of inhibitors (eg, acquired versus inherited hemophilia)
  • Thrombin clotting time and plasma concentration of fibrinogen – normal in hemophilia A and B

Laboratory Testing for Hemophilia

  • FVIII activity level – decreased in hemophilia A and acquired hemophilia A
  • FIX activity level – decreased in hemophilia B and acquired hemophilia B
    • Not reliable for carrier status detection in females
    • Measurement in neonate may need to be repeated when family history of mild disease exists
  • von Willebrand factor (VWF) level – normal
    • Because VWF is a carrier for FVIII, von Willebrand disease (VWD) should be ruled out in patients with decreased FVIII levels
    • A rare subtype of VWD (type 2N) has isolated low FVIII activity with normal VWF level and mimics hemophilia A
      • Specialized coagulation or genetic testing can be used to distinguish these disorders
  • Bethesda assay – used as reflex test to detect presence of inhibitors versus factor deficiency and to monitor treated hemophilia patients for the development of an inhibitor
  • Genetic testing
    • Patient risk should be calculated by a clinical geneticist using laboratory results and family history
    • Indications
      • Confirm the causative F8 or F9 gene variant in affected individuals
      • Determine carrier status in at-risk females
  • At-risk fetus
    • Third trimester amniocentesis should be considered for confirmation of affected male fetus
    • Uncontaminated cord blood should be used at birth to establish diagnosis if not done previously
    • Order FVIII and FIX assays in addition to activated PTT; FIX assays are difficult to interpret in neonates


  • Improved prognosis with the advent of FVIII and FIX replacement
  • Major disability from bleeding – joint disease
  • Leading cause of death from bleeding – intracranial hemorrhage

Differential Diagnosis

  • Individuals receiving treatment for hemophilia are at risk for development of inhibitors
    • Development of inhibitors not necessarily accompanied by clinical signs, so monitoring is required
  • Indications for testing
    • Prior to elective invasive procedures
    • Suboptimal response to factor concentrate replacement
    • Before and after switching factor products
    • 2-3 weeks after intensive treatment or surgery
    • Severe hemophilia A and B
      • Every third exposure day or every 3 months until 20 exposure days have been reached
    • Hemophilia A
      • Once or twice annually throughout a patient’s life
    • Hemophilia B
      • Testing unnecessary after 150 exposure days unless presence of inhibitor clinically suspected
  • Laboratory testing
    • Factor assays
      • Consider confirmation of low factor activity using a chromogenic assay since a number of interfering substances (eg, heparin, lupus anticoagulants) can interfere with the first-line clot-based factor assays, and some forms of hemophilia have clinically significant discrepancies between clot-based and chromogenic assay results
      • Note that some of the newer extended half-life factor replacement products are not accurately measured in some types of factor assays (depends on the combination of product and assay methodology)
        • If these products are being used, need to confirm which type of factor assay is appropriate for the product
    • Bethesda assay or Nijmegen-Bethesda assay  
    • Activated partial thromboplastin time – initial test but not appropriate for specific diagnostic testing
    • Barriers to testing
      • Cost
      • Availability


  • Incidence
    • Hemophilia A – 1/4,000-5,000 male births worldwide; rare in females
    • Hemophilia B – 1/25,000 male births worldwide; rare in females
    • Acquired hemophilia – 1-2/million worldwide
      • <1/million in children
  • Age
    • Severe disease – usually detected in first year of life
    • Moderate disease – detected before age 5
    • Mild disease – detected later in life
    • Acquired disease – bimodal peaks at 20-40 years and 60-90 years
  • Types
    • Hemophilia A – FVIII deficiency
    • Hemophilia B – FIX deficiency
    • Acquired hemophilia – autoimmune disorder caused by antibodies to FVIII or, rarely, FIX


  • Clinical Presentation

    • Hemophilia A is clinically indistinguishable from hemophilia B
    • Excessive bleeding – occurs spontaneously or from trivial injury
      • Common bleeding manifestations – hemarthrosis, hematomas, gastrointestinal bleeding, genitourinary bleeding
    • Frequency and severity of excessive bleeding based on FVIII or FIX activity
      • Mild disease (6-40% factor activity) – bleeding may occur with major trauma or surgery; no spontaneous bleeding
        • Often not diagnosed until adulthood
        • Carrier females – 10% have mild disease (<40% factor activity) and are at risk for excessive bleeding
      • Moderate disease (1-5% factor activity) – bleeding may occur with minimal trauma or minor surgery; spontaneous bleeding rare
        • Typically diagnosed by 5 years
      • Severe disease (<1% factor activity) – high risk of severe, spontaneous bleeding
        • Usually diagnosed in first year of life due to spontaneous muscle and joint bleeding
    • Acquired disease occurs rarely in children and the bleeding patterns can be different than in inherited disease (greater frequency of mucocutaneous bleeding)
    Tests generally appear in the order most useful for common clinical situations. Click on number for test-specific information in the ARUP Laboratory Test Directory.

    CBC with Platelet Count and Automated Differential 0040003
    Method: Automated Cell Count/Differential

    Prothrombin Time 0030215
    Method: Electromagnetic Mechanical Clot Detection

    Partial Thromboplastin Time 0030235
    Method: Electromagnetic Mechanical Clot Detection

    Fibrinogen 0030130
    Method: Electromagnetic Mechanical Clot Detection

    Thrombin Time with Reflex to Thrombin Time 1:1 Mix 0030260
    Method: Electromagnetic Mechanical Clot Detection

    Factor VIII, Activity 0030095
    Method: Electromagnetic Mechanical Clot Detection

    Factor VIII Activity with Reflex to Bethesda Quantitative, Factor VIII 0030026
    Method: Electromagnetic Mechanical Clot Detection

    von Willebrand Panel 0030125
    Method: Electromagnetic Mechanical Clot Detection/Platelet Agglutination/Microlatex Particle-Mediated Immunoassay

    Factor IX, Activity 0030100
    Method: Electromagnetic Mechanical Clot Detection

    Factor IX Activity with Reflex to Bethesda Quantitative, Factor IX 0030032
    Method: Electromagnetic Mechanical Clot Detection

    Hemophilia A (F8) 2 Inversions with Reflex to Sequencing and Reflex to Deletion/Duplication 2001614
    Method: Inverse Polymerase Chain Reaction/Sequencing/Multiplex Ligation-dependent Probe Amplification


    Diagnostic errors can occur due to rare sequence variations

    Regulatory region and deep intronic variants, other than the F8 intron 22-A and intron 1 inversions, will not be detected

    Deletions/duplications in exon 23 will not be detected.

    Hemophilia B (F9) Sequencing and Deletion/Duplication 2010494
    Method: Polymerase Chain Reaction/Sequencing/Multiplex Ligation-dependent Probe Amplification


    Diagnostic errors can occur due to rare sequence variations

    Regulatory region variants and deep intronic variants will not be detected

    The breakpoints of large deletions/duplications will not be determined

    Large deletions/duplications in exon 1 may not be detected

    Variants in genes other than F9 will not be detected


    Chalmers E, Williams M, Brennand J, Liesner R, Collins P, Richards M, Paediatric Working Party of United Kingdom Haemophilia Doctors' Organization. Guideline on the management of haemophilia in the fetus and neonate. Br J Haematol. 2011; 154(2): 208-15. PubMed

    de Moerloose P, Fischer K, Lambert T, Windyga J, Batorova A, Lavigne-Lissalde G, Rocino A, Astermark J, Hermans C. Recommendations for assessment, monitoring and follow-up of patients with haemophilia. Haemophilia. 2012; 18(3): 319-25. PubMed

    James AH. Diagnosis and management of women with bleeding disorders--international guidelines and consensus from an international expert panel. Haemophilia. 2011; 17 Suppl 1: 3-5. PubMed

    MASAC Recommendations on Standardized Testing and Surveillance for Inhibitors in Patients with Hemophilia A and B. National Hemophilia Foundation. New York , NY [Accessed: May 2017]

    MASAC Statement Regarding Use of Various Clotting Factor Assays to Monitor Factor Replacement Therapy. National Hemophilia Foundation. New York , NY [Accessed: May 2017]

    WFH Guidelines for the Management of Hemophilia. World Federation of Hemophilia. Montréal, Canada [Updated: Aug 2014; Accessed: Feb 2016]

    General References

    Boylan B, Rice AS, Neff AT, Manco-Johnson MJ, Kempton CL, Miller CH, Hemophilia Inhibitor Research Study Investigators. Survey of the anti-factor IX immunoglobulin profiles in patients with hemophilia B using a fluorescence-based immunoassay. J Thromb Haemost. 2016; 14(10): 1931-1940. PubMed

    Coppola A, Favaloro EJ, Tufano A, Di Minno MN, Cerbone AM, Franchini M. Acquired inhibitors of coagulation factors: part I-acquired hemophilia A. Semin Thromb Hemost. 2012; 38(5): 433-46. PubMed

    de Brasi C, El-Maarri O, Perry DJ, Oldenburg J, Pezeshkpoor B, Goodeve A. Genetic testing in bleeding disorders. Haemophilia. 2014; 20 Suppl 4: 54-8. PubMed

    Fijnvandraat K, Cnossen MH, Leebeek FW, Peters M. Diagnosis and management of haemophilia. BMJ. 2012; 344: e2707. PubMed

    Franchini M, Favaloro EJ, Lippi G. Mild hemophilia A. J Thromb Haemost. 2010; 8(3): 421-32. PubMed

    Franchini M, Zaffanello M, Lippi G. Acquired hemophilia in pediatrics: a systematic review. Pediatr Blood Cancer. 2010; 55(4): 606-11. PubMed

    Hemophilia - Bleeding and Clotting Disorders Surveillance. Centers for Disease Control and Prevention. Atlanta, GA [Last updated: Jul 2014; Accessed: Jan 2017]

    Mulliez SM, Vantilborgh A, Devreese KM. Acquired hemophilia: a case report and review of the literature. Int J Lab Hematol. 2014; 36(3): 398-407. PubMed

    Verbruggen B, Meijer P, Novákova I, Van Heerde W. Diagnosis of factor VIII deficiency. Haemophilia. 2008; 14 Suppl 3: 76-82. PubMed

    Wagenman BL, Townsend KT, Mathew P, Crookston KP. The laboratory approach to inherited and acquired coagulation factor deficiencies. Clin Lab Med. 2009; 29(2): 229-52. PubMed

    References from the ARUP Institute for Clinical and Experimental Pathology®

    Flanders MM, Crist RA, Roberts WL, Rodgers GM. Pediatric reference intervals for seven common coagulation assays. Clin Chem. 2005; 51(9): 1738-42. PubMed

    Heikal NM, Murphy KK, Crist RA, Wilson AR, Rodgers GM, Smock KJ. Elevated factor IX activity is associated with an increased odds ratio for both arterial and venous thrombotic events. Am J Clin Pathol. 2013; 140(5): 680-5. PubMed

    Miranda GG, Rodgers GM. Treatment of an acquired factor VIII inhibitor with sequential recombinant factor VIIa and FEIBA. Haemophilia. 2009; 15(1): 383-5. PubMed

    Nance D, Rodgers GM. Switching haemophilia products and inhibitor risk: a United States' perspective Eur J Haematol. 2015; 94(4): 283. PubMed

    Peerschke EI, Castellone DD, Ledford-Kraemer M, Van Cott EM, Meijer P, NASCOLA Proficiency Testing Committee. Laboratory assessment of factor VIII inhibitor titer: the North American Specialized Coagulation Laboratory Association experience. Am J Clin Pathol. 2009; 131(4): 552-8. PubMed

    Rodgers GM. Prothrombin complex concentrates in emergency bleeding disorders. Am J Hematol. 2012; 87(9): 898-902. PubMed

    Sborov DW, Rodgers GM. How I manage patients with acquired haemophilia A. Br J Haematol. 2013; 161(2): 157-65. PubMed

    Yaish H, Rodgers GM. A haemophilia B patient with severe burn injury: increased requirement for factor IX replacement therapy associated with venous thromboembolism. Haemophilia. 2008; 14(3): 607-9. PubMed

    Medical Reviewers

    Last Update: October 2017