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HelpTest Code GNHMB Hemophilia B, F9 Gene, Next-Generation Sequencing, Varies
Ordering Guidance
For male patients, this test should only be considered if clinical and family history, initial coagulation screens, and/or initial activity tests indicate a diagnosis of hemophilia B. For female patients, this test should only be considered if there is a confirmed diagnosis of hemophilia B in a family member or the patient has abnormally low factor IX (FIX) activity.
This test does not measure FIX activity levels. For assessment of FIX activity, F_9 / Coagulation Factor IX Activity Assay, Plasma.
For individuals with bleeding symptoms and no known personal or family history of hemophilia B, consider ALBLD / Bleeding Diathesis Profile, Limited, Plasma or the specific factor assays.
If genetic testing for hereditary bleeding disorders using a larger panel is desired, both a 6-gene focused bleeding panel and a 25-gene comprehensive bleeding panel are available. For more information see GNBLF / Bleeding Disorders, Focused Gene Panel, Next-Generation Sequencing, Varies or GNBLC / Bleeding Disorders, Comprehensive Gene Panel, Next-Generation Sequencing, Varies.
Testing for the F9 gene as part of a customized panel is available. For more information see CGPH / Custom Gene Panel, Hereditary, Next-Generation Sequencing, Varies.
Targeted testing for familial variants (also called site-specific or known variants testing) is available for the F9 gene. See FMTT / Familial Variant, Targeted Testing, Varies. To obtain more information about this testing option, call 800-533-1710.
Additional Testing Requirements
All prenatal specimens must be accompanied by a maternal blood specimen; order MATCC / Maternal Cell Contamination, Molecular Analysis, Varies on the maternal specimen as this must be a different order number than the prenatal specimen.
Shipping Instructions
Specimen preferred to arrive within 96 hours of collection.
Necessary Information
Hemophilia B Patient Information is required. Testing may proceed without the patient information; however, the information aids in providing a more thorough interpretation. Ordering providers are strongly encouraged to fill out the form and send with the specimen.
Specimen Required
Patient Preparation: A previous bone marrow transplant from an allogenic donor will interfere with testing. For instructions for testing patients who have received a bone marrow transplant, call 800-533-1710.
Submit only 1 of the following specimens:
Specimen Type: Whole blood
Container/Tube:
Preferred: Lavender top (EDTA)
Acceptable: Yellow top (ACD)
Specimen Volume: 3 mL
Collection Instructions:
1. Invert several times to mix blood.
2. Send whole blood specimen in original tube. Do not aliquot.
Specimen Stability Information: Ambient (preferred) 4 days/Refrigerated
Prenatal Specimens
Due to its complexity, consultation with the laboratory is required for all prenatal testing; call 800-533-1710 to speak to a genetic counselor.
Specimen Type: Amniotic fluid
Container/Tube: Amniotic fluid container
Specimen Volume: 20 mL
Specimen Stability Information: Refrigerated (preferred)/Ambient
Additional information:
1. A separate culture charge will be assessed under CULAF / Culture for Genetic Testing, Amniotic Fluid.
2. All prenatal specimens must be accompanied by a maternal blood specimen; order MATCC / Maternal Cell Contamination, Molecular Analysis, Varies on the maternal specimen.
Specimen Type: Chorionic villi
Container/Tube: 15-mL tube containing 15 mL of transport media
Specimen Volume: 20 mg
Specimen Stability Information: Refrigerated
Additional Information: 1. A separate culture charge will be assessed under CULFB / Fibroblast Culture for Biochemical or Molecular Testing.
2. All prenatal specimens must be accompanied by a maternal blood specimen; order MATCC / Maternal Cell Contamination, Molecular Analysis, Varies on the maternal specimen.
Acceptable:
Specimen Type: Confluent cultured cells
Container/Tube: T-25 flask
Specimen Volume: 2 Flasks
Collection Instructions: Submit confluent cultured cells from another laboratory.
Specimen Stability Information: Ambient (preferred)/Refrigerated
Additional Information:
All prenatal specimens must be accompanied by a maternal blood specimen; order MATCC / Maternal Cell Contamination, Molecular Analysis, Varies on the maternal specimen.
Forms
1. Hemophilia B Patient Information (T518) is required.
2. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available:
-Informed Consent for Genetic Testing (T576)
-Informed Consent for Genetic Testing (Spanish) (T826)
3. If not ordering electronically, complete, print, and send an Coagulation Test Request (T753) with the specimen.
Useful For
Confirming a clinical diagnosis of hemophilia B in affected male patients with the identification of a disease-causing variant in the F9 gene
Determining the disease-causing alteration within the F9 gene to delineate the underlying molecular defect in a male patient with a laboratory diagnosis of hemophilia B
Identifying the causative alteration for prognostic and genetic counseling purposes
Assessing hemophilia B carrier status for female patients with a family history of hemophilia B
Prenatal testing for hemophilia B when a familial F9 variant has been previously identified in a family member
Disease States
- Hemophilia B
Reflex Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| CULFB | Fibroblast Culture for Genetic Test | Yes | No |
| CULAF | Amniotic Fluid Culture/Genetic Test | Yes | No |
| MATCC | Maternal Cell Contamination, B | Yes | No |
Special Instructions
Method Name
Sequence Capture and Targeted Next-Generation Sequencing (NGS) followed by Polymerase Chain Reaction (PCR) and Sanger Sequencing
Reporting Name
F9 Gene, Full Gene NGSSpecimen Type
VariesSpecimen Minimum Volume
Blood: 1 mL; Amniotic fluid: 10 mL; Other specimen types: see Specimen Required
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Varies | Varies | ||
Reject Due To
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.Clinical Information
Hemophilia B (HB) is a hereditary bleeding disorder associated with germline variants in the F9 gene. It is inherited in an X-linked recessive manner with variable expressivity and is estimated to affect 1 in 30,000 live male births.(2,3)
HB is characterized by a deficiency in clotting factor IX (FIX), a vitamin K–dependent enzyme essential for clot formation. Symptomatic male patients may experience mild to severe bleeding problems, including excessive bruising, prolonged epistaxis, post-operative bleeding, hemarthrosis, deep-muscle hematomas, and intracranial or gastrointestinal tract bleeding. Female carriers are not typically affected but some may experience increased bleeding tendencies, especially after medical procedures and surgery. Note that FIX activity may not correlate with the severity of symptoms in female patients.(2-7)
Acquired (nongenetic) hemophilia B is quite rare; most cases result from the development of autoantibodies toward FIX. Causes to exclude prior to genetic testing include vitamin K deficiency, autoimmune disorders, malignancies, and infections such as HIV and hepatitis B.(8)
The World Federation of Hemophilia provides guidelines regarding diagnosis, management, and laboratory testing for individuals with HB.(9)
Reference Values
An interpretive report will be provided.
Day(s) Performed
Varies
Report Available
28 to 42 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
81238
88233-Tissue culture, skin, solid tissue biopsy (if appropriate)
88240-Cryopreservation (if appropriate)
88235-Amniotic fluid culture (if appropriate)
81265-Maternal cell contamination (if appropriate)