Prenatal testing for hemophilia A caused by a familial F8 gene intron 22-A or intron 1 inversion.
- Patient Preparation
- Fetal Specimen: Two T-25 flasks at 80% confluent of cultured amniocytes. If the client is unable to culture amniocytes, this can be arranged by contacting ARUP Client Services at (800) 522-2787.
Maternal Specimen: Lavender (EDTA) or yellow (ACD Solution A or B).
- Specimen Preparation
- Cultured Amniocytes: Fill flasks with culture media. Transport two T-25 flasks at 80% confluent of cultured amniocytes. Backup cultures must be retained at the client's institution until testing is complete.
Maternal Specimen: Transport 3 mL whole blood.
- Storage/Transport Temperature
- Fetal Specimens: CRITICAL ROOM TEMPERATURE. Must be received within 48 hours of shipment due to lability of cells.
Maternal Specimen: Room temperature. Ship with the fetal specimen.
- Unacceptable Conditions
- Maternal sample is recommended for proper test interpretation. Order Maternal Cell Contamination, Maternal Specimen. This can be arranged by contacting ARUP genetic counselors at (800) 242-2787 ext. 2141. Patient History Form is available on the ARUP Web site or by contacting ARUP Client Services.
- Fetal Specimen: Ambient: 48 hours; Refrigerated: Unacceptable; Frozen: Unacceptable
Maternal Specimen: Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable
Characteristics: Severe deficiency of factor VIII clotting activity leading to spontaneous joint or deep muscle bleeding. Moderate to mild deficiency is associated with prolonged bleeding after tooth extractions, surgery, or injuries and recurrent or delayed wound healing.
Incidence: 1 in 4,000-5,000 live male births worldwide, rare in females.
Inheritance: X-linked recessive. Of simplex cases, 85 percent of mothers are carriers and 10-15 percent of boys have a de novo mutation.
Penetrance: 100 percent in males and 10 percent in females.
Cause: Deleterious F8 gene mutations.
Clinical Sensitivity: 51 percent of mutations causing severe hemophilia A are detected by F8 inversion testing. This assay does not detect F8 mutations associated with mild or moderate hemophilia A in males.
Methodology: Intron 22-A and intron 1 inversions detected by inverse PCR and electrophoresis.
Analytical Sensitivity and Specificity: 99 percent.
Limitations: Diagnostic errors can occur due to rare sequence variations. F8 mutations, other than the F8 intron 22-A and intron 1 inversions, will not be detected.
For quality assurance purposes, ARUP Laboratories will provide a confirmation of the above result at no charge. Following delivery, please collect a cord blood sample from the infant in a lavender (EDTA) or yellow (ACD Solution A or B) top tube and transport 1mL cord blood at 2-8 °C. Please specify on the test request form that this is a confirmatory study to be performed at no charge. Please provide the mother's name for specimen identification purposes.
Counseling and informed consent are recommended for genetic testing. Consent forms are available online.
|Component Test Code*||Component Chart Name||LOINC|
|0050548||Maternal Contamination Study Fetal Spec||59266-7|
|0050612||Maternal Contam Study, Maternal Spec||31208-2|
|2001758||F8 INV FE Specimen||31208-2|
|2001761||Hemophilia A (F8) Inversions Interp||82343-5|
- Fetal Carrier Detection of Hemophilia A
- Fetal DNA Analysis for Hemophilia A
- Fetal Factor VIII Deficiency assay
- Fetal Hemophilia A Carrier Detection and Prenatal Diagnosis