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Test Code F9MAP Hemophilia B, F9 Gene Mutation Analysis, Amniotic Fluid or Chorionic Villus Sampling

Useful For

Prenatal testing for a pathogenic mutation in the F9 gene in a fetus with a strong, confirmed family history of congenital hemophilia B (factor IX activity deficiency) in the exceptional circumstance where a familial mutation cannot be otherwise ascertained

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

Testing Algorithm

If amniotic fluid (nonconfluent cultured cells) is received, amniotic fluid culture/genetic test will be added and charged separately. If chorionic villus specimen (nonconfluent cultured cells) is received, fibroblast culture for genetic test will be added and charged separately. For any prenatal specimen that is received, maternal cell contamination studies will be added. A maternal peripheral blood sample is required to perform this test.

 

The following algorithms are available in Special Instructions:

-Hemophilia Carrier Testing Algorithm

-Hemophilia Testing Algorithm

Method Name

Polymerase Chain Reaction (PCR)/Fluorescent DNA Sequencing

(PCR is utilized pursuant to a license agreement with Roche Molecular Systems, Inc.)

Reporting Name

F9 Gene Mut Analysis, AF or CVS

Specimen Type

Varies


Specimen Required


Forms:

1. Hemophilia B: Patient Information (T518) in Special Instructions is required. Fax the completed form to 507-284-8286.

2. New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (T576) is available in Special Instructions.

3. If not ordering electronically, complete, print, and send a Coagulation Test Request Form (T753) with the specimen (http://www.mayomedicallaboratories.com/it-mmfiles/coagulation-test-request-form.pdf)

 

Advise Express Mail or equivalent if not on courier service.

 

Results will be reported and also telephoned or faxed, if requested.

 

Due to the complexity of prenatal testing, consultation with the laboratory is required for all prenatal testing. Prenatal specimens can be sent Monday through Thursday and must be received by 5 p.m. CST on Friday in order to be processed appropriately. All prenatal specimens must be accompanied by a maternal peripheral blood specimen. Order MATCC / Maternal Cell Contamination, Molecular Analysis on the maternal specimen.

 

A. For the purposes of maternal cell contamination studies (MCC), submit the following specimen type from the mother in addition to 1 of the 3 accepted fetal specimen types:

 

Specimen Type: Peripheral blood

Container/Tube:

Preferred: Yellow top (ACD solution B)

Acceptable: EDTA or sodium citrate

Specimen Volume: 6 mL

Collection Instructions:

1. Invert several times to mix blood.

2. Send specimen in original tube.

Specimen Stability Information: Ambient (preferred)/Refrigerated

 

B. For the purposes of prenatal testing of the fetus, submit only 1 of the following specimens:

 

Specimen Type: Amniotic fluid

Container/Tube: Amniotic fluid container

Specimen Volume: 5-10 mL

Collection Instructions:

1. Optimal timing for specimen collection is during 14 to 18 weeks of gestation, but specimens collected at other weeks of gestation are also accepted.

2. Discard the first 2 mL of amniotic fluid. If the culture will be performed in conjunction with chromosome analysis and alpha-fetoprotein, a total of approximately 25 mL to 30 mL will be needed for the combined studies.

Specimen Stability Information: Ambient (preferred) <24 hours/Refrigerated

 

Specimen Type: Chorionic villi

Container/Tube: 15-mL tube containing 15 mL of transport media

Specimen Volume: 20-30 mg

Collection Instructions:

1. Collect specimen by the transabdominal or transcervical method.

2. Transfer the chorionic villi specimen to a Petri dish containing transport medium (Supply T095).

3. Using a stereomicroscope and sterile forceps, assess the quality and quantity of the villi and remove any blood clots and maternal decidua.

Specimen Stability Information: Refrigerated (preferred) <24 hours/Ambient

 

Specimen Type: Confluent cultured cells

Container/Tube: T-25 flask

Specimen Volume: 2 Flasks approximately 90% confluent

Collection Instructions: Submit confluent cultured cells from another laboratory

Specimen Stability Information: Ambient (preferred) <24 hours/Refrigerated

Additional Information:

1. Place the tubes in a Styrofoam container (T329).

2. Fill remaining space with packing material.

3. Unavoidably, about 1% to 2% of mailed-in specimens are not viable.

4. Bloody specimens are undesirable.

5. If the specimen does not grow in culture, you will be notified within 7 days of receipt.

6. There will be no culture charge.


Specimen Minimum Volume

Amniotic fluid: 10 mL / Chorionic Villi: 5 mg

Specimen Stability Information

Specimen Type Temperature Time
Varies Varies

Reject Due To

Hemolysis

NA

Lipemia

NA

Icterus

NA

Other

NA

Clinical Information

Hemophilia B, factor IX deficiency, is an X-linked recessive bleeding disorder with an incidence of about 1 per 30,000 live male births. It occurs as a result of mutations in the factor IX (F9) gene. As many as one-third of hemophiliacs have no affected family members, which reflects a high mutation rate in the F9 gene (ie, de novo mutations). Hemophilia B affects males; however, all male offspring from an affected male will be normal. Although all female offspring of affected males will be obligatory carriers, they rarely have symptomatic bleeding. In contrast, female offspring of female carriers of hemophilia B have a 50% chance of being carriers themselves and each male offspring has a 50% chance of being affected.

 

Based on factor IX activity, hemophilia B is classified as severe (factor IX activity <1%), moderate (factor IX activity 1%-5%), or mild (factor IX activity >5%-40%). In males, a low factor IX activity level establishes the diagnosis of hemophilia B. However, the wide range of normal factor IX activity precludes an accurate assessment of carrier status in females, thus making molecular testing essential in assessment of carrier status.

 

Inhibitors to factor IX activity are estimated to occur in 5% to 8% of patients, much less than that of hemophilia A. Inhibitor risk correlates with genotype and typically occurs in patients with either partial or total deletions of the F9 gene or in certain nonsense mutations that result in no circulating factor IX:antigen. More recently, it has been observed that a subset of patients with such mutations may be at risk of experiencing anaphylactic reactions to the factor IX replacement therapy.

Reference Values

An interpretive report will be issued that will include specimen information, assay information, background information, and conclusions based on the test results (ie, information about the mutation and carrier status).

Interpretation

An interpretive report will be provided.

Clinical Reference

1. Yoshitake S, Schach BG, Foster DC, et al: Complete nucleotide sequence of the gene for human factor IX (antihemophilic factor B). Biochemistry 1985;24(14):3736-3750

2. Giannelli F, Green PM, Sommer SS, et al: Haemophilia B: database of point mutations and short additions and deletions-eighth edition. Nucleic Acids Res 1998;26(1):265-268

3. Ketterling RP, Bottema CD, Phillips JA 3rd, Sommer SS: Evidence that descendants of three founders constitute about 25% of hemophilia B in the United States. Genomics 1991;10(4):1093-1096

Day(s) and Time(s) Performed

Monday through Friday

Analytic Time

28 days

Performing Laboratory

Mayo Medical Laboratories in Rochester

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

81405

LOINC Code Information

Test ID Test Order Name Order LOINC Value
F9MAP F9 Gene Mut Analysis, AF or CVS In Process

 

Result ID Test Result Name Result LOINC Value
37880 F9 Reason for Referral In Process
37881 F9 Mutation Analysis Method In Process
37882 F9 Mutation Analysis, AF or CVS In Process
37883 F9 Mutation Analysis Specimen Type In Process
37884 F9 Mutation Analysis Interpretation In Process
37885 F9 Mutation Analysis Reviewed By In Process