Home
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.
Secondary ID
619117Useful 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
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 |
Testing Algorithm
The clinical workup for hemophilia B in symptomatic male patients should begin with special coagulation testing for factor IX (FIX) activity. Genetic testing is indicated if FIX activity is less than 40% of normal (Note: reference range may vary depending on the locally established reference range) and von Willebrand factor antigen testing is normal. For more information see Hemophilia Testing Algorithm.
FIX clotting activity does not correlate as well with bleeding severity in female patients, and therefore is unreliable in the detection of female carriers of hemophilia B. Carrier status is determined by identification of a heterozygous disease-causing variant in F9 by molecular genetic testing. For female patients with a suspected or confirmed diagnosis of hemophilia B in a family member, carrier testing is recommended as specified by the Hemophilia Carrier Testing Algorithm.(1-3)
Acquired (nongenetic) causes of hemophilia B that should be excluded prior to genetic testing include vitamin K deficiency autoimmune disorders, malignancy, and infections such as HIV and hepatitis B.
For prenatal specimens only:
Prenatal genetic testing is not routinely performed without the prior identification of a familial hemophilia alteration in an affected male relative or a female relative who is a confirmed carrier of the alteration. Requests for this prenatal testing without a known familial alteration are performed at the discretion of the Molecular Hematopathology Laboratory Director.
-If amniotic fluid (nonconfluent cultured cells) is received, amniotic fluid culture/genetic test will be added at an additional charge.
-If chorionic villus specimen (nonconfluent cultured cells) is received, fibroblast culture for genetic test will be added at an additional charge.
For any prenatal specimen that is received, maternal cell contamination testing will be performed at an additional charge.
Special Instructions
Method Name
Sequence Capture and Targeted Next-Generation Sequencing (NGS) followed by Polymerase Chain Reaction (PCR) and Sanger Sequencing
Specimen 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.Reference Values
An interpretive report will be provided.
Interpretation
All detected variants are evaluated according to American College of Medical Genetics and Genomics recommendations.(10) Variants are classified based on known, predicted, or possible pathogenicity and reported with interpretive comments detailing their potential or known significance.
Method Description
Next-generation sequencing (NGS) and/or Sanger sequencing are performed to test for the presence of variants in coding regions and intron/exon boundaries of the F9 gene, as well as some other regions that have known disease-causing variants. The human genome reference GRCh37/hg19 build was used for sequence read alignment. At least 99% of the bases are covered at a read depth over 30X. Sensitivity is estimated at above 99% for single nucleotide variants, above 94% for deletions-insertions (delins) less than 40 base pairs (bp), above 95% for deletions up to 75 bp, and insertions up to 47 bp. NGS and/or a polymerase chain reaction-based quantitative method is performed to test for the presence of deletions and duplications in the F9 gene.
There may be regions of the F9 gene that cannot be effectively evaluated by sequencing or deletion and duplication analysis as a result of technical limitations of the assay, including regions of homology, high guanine-cytosine (GC) content, and repetitive sequences.(Unpublished Mayo method)
The reference transcript for the F9 gene is NM_000133.4. Reference transcript numbers may be updated due to transcript re-versioning. Always refer to the final patient report for gene transcript information referenced at the time of testing. Confirmation of select reportable variants may be performed by alternate methodologies based on internal laboratory criteria.
Day(s) Performed
Varies
Report Available
28 to 42 daysSpecimen Retention Time
Whole blood: 2 weeks (if available); Extracted DNA: 3 months; Amniotic fluid, cultured amniocytes, chorionic villi, cultured chorionic villi: 1 monthPerforming Laboratory
Mayo Clinic Laboratories in Rochester
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)
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| GNHMB | F9 Gene, Full Gene NGS | 93811-8 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 619118 | Test Description | 62364-5 |
| 619119 | Specimen | 31208-2 |
| 619120 | Source | 31208-2 |
| 619121 | Result Summary | 50397-9 |
| 619122 | Result | 82939-0 |
| 619123 | Interpretation | 59465-5 |
| 619124 | Additional Results | 82939-0 |
| 619125 | Resources | 99622-3 |
| 619126 | Additional Information | 48767-8 |
| 619127 | Method | 85069-3 |
| 619128 | Genes Analyzed | 82939-0 |
| 619129 | Disclaimer | 62364-5 |
| 619130 | Released By | 18771-6 |