Clinics and Departments

Laboratory Services

Lab Dept:

Coagulation

Test Name:

HEMOPHILIA A MOLECULAR INVERSION

General Information

Lab Order Codes:

HAMI

Synonyms:

Carrier Detection of Hemophilia A; DNA Analysis for Hemophilia A; Factor VIII Deficiency; Factor VIII Inversion; Hemophilia A Carrier Detection and Prenatal Diagnosis; Severe Hemophilia

CPT Codes:

81403 – F8, inversion analysis, intron 1 and 22A (Molecular Pathology, Level 4)

Test Includes:

Detects the common inversion mutation with factor VIII gene. Approximately 45% of affected males with severe hemophilia A have been shown to have this inversion.

It is recommended that this test be used first on an affected family member before carrier testing is done for at risk individuals.

Logistics

Test Indications:

Useful for identifying the disease-causing mutation in males with severe hemophilia A. Determining hemophilia A-carrier status for individuals with family history of F8 intron 22 inversions.

Lab Testing Section:

Coagulation - Sendouts

Referred to:

Mayo Medical Laboratories (MML Test#: HAPB/80297)

Phone Numbers:

MIN Lab: 612-813-6280

STP Lab: 651-220-6550

Test Availability:

Daily, 24 hours. Specimens received Monday – Friday at noon will be processed for the run starting the following Monday. Specimens received Friday through Saturday will be set up a week from the following Monday.

Turnaround Time:

14 - 21 days, test set up as described under Test Availability.

Special Instructions:

Specimens must arrive at reference lab within 96 hours of collection.

All specimens must include a “Molecular Genetics Congenital Disorders Request Form” (Mayo Supply T521- obtain from lab) with information including relevant clinical and family history information in order to provide correct interpretation of test results. If informed consent is required, please submit an "Informed Consent for DNA Testing" (Supply T576-obtain from lab) with the specimen.

The analysis will be set up only after all specimens (from each family member) are received.

A prior consultation with a medical geneticist is recommended.

Specimen

Specimen Type:

Submit only one (1) of the following:

Amniotic Fluid or Blood/Maternal Blood or Chorionic Villus (CVS)

Container:

Blood: Lavender top (EDTA) or Yellow top (ACD) tube
Amniotic fluid:
Conical tubes
Chorionic Villi:
Contact the laboratory

Draw Volume:

Blood/Maternal Blood: Draw 3 mL (Minimum: 1 mL) blood in a Lavender top or Yellow top tube

Please call Children’s Hospitals and Clinics before collecting the amniotic fluid specimen. All amniotic fluid specimens must be accompanied by a maternal blood specimen. This is necessary for maternal cell contamination testing (no extra charge).

Chorionic Villus: Please call Children's Hospitals and Clinics before collecting the chorionic villus specimen (CVS). All CVS must be accompanied by a maternal blood specimen. This is necessary for maternal cell contamination testing (no extra charge).

Processed Volume:

Forward entire specimen to reference lab

Collection:

Blood/Maternal Blood: 3 mL (Minimum: 1 mL) whole blood. Gently invert several times to mix. Send specimen to the lab at room temperature immediately.

Amniotic Fluid: Bloody specimens are undesirable. Obtain specimen during 14th – 17th week of gestation. Draw 20 mL (Minimum: 10 mL) of amniotic fluid in a sterile syringe. Remove needle and transfer the specimen into 2 screw-capped, sterile 15-mL centrifuge tubes. Label appropriately. Alternatively, MML will accept two T-25 flasks of confluent cultured cells from another laboratory sent at ambient temperature.

Chorionic Villus: Obtain 20 mg (Minimum: 5 gm). Send specimen refrigerated in transport media in 15-mL centrifuge tube. Specimen cannot be frozen. Label appropriately.

Special Processing:

Lab Staff: Specimens should remain in original collection containers. Forward specimen(s) and accompanying paperwork to reference laboratory promptly at ambient/room temperature. Do Not freeze.

Patient Preparation:

None

Sample Rejection:

If a sample is received at the wrong temperature or in the wrong anticoagulant, it will be noted at MML. Specimens received at Children’s that are unlabeled or mislabeled will be rejected.

Interpretive

Reference Range:

An interpretive report will be issued which will include a risk analysis. The report will include specimen information, pedigree, assay information, background information, and estimate of carrier risk based on test results.

Critical Values:

N/A

Limitations:

The inversion found in this direct analysis is found about 45% of individuals with severe hemophilia A, which may be uninformative for a number of families.

The absence of an inversion does not exclude the presence of another type of mutation in the Factor VIII gene.

Linkage analysis is recommended to determine carrier status in those families who do not demonstrate the inversion and those with mild or moderate hemophilia A.

Any error in the diagnosis or in the pedigree provided will lead to an erroneous segregation pattern and an incorrect interpretation of the results.

Medical genetic or hemophilia center consultation is available for all DNA diagnosis cases and is particularly indicated in complex cases or in situations in which the diagnosis is atypical or uncertain.

Methodology:

Intron 22 inversions within the factor VIII gene are identified by Southern blot analysis.

References:

Mayo Medical Laboratories Web Page September 2013
(800) 533-1710

Updates:

2/12/2013: CPT update



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