Genetic test on fetal specimens for prenatal detection of HbS, HbC, and HbE variants.
- Patient Preparation
- Fetal Specimen: Two T-25 flasks at 80% confluency of cultured amniocytes. If the client is unable to culture amniocytes, this can be arranged by contacting ARUP Client Services at (800) 522-2787. Or amniotic fluid.
AND Maternal Cell Contamination Specimen: Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).
- Specimen Preparation
- Cultured Amniocytes: Fill flasks with culture media. Transport two T-25 flasks at 80% confluency of cultured amniocytes. Backup cultures must be retained at the client's institution until testing is complete.
OR Amniotic Fluid: Transport 10 mL unspun fluid. (Min: 5 mL)
AND Maternal Cell Contamination Specimen: Transport 3 mL whole blood. (Min: 1 mL)
- Storage/Transport Temperature
- Cultured Amniocytes: CRITICAL ROOM TEMPERATURE. Must be received within 48 hours of shipment due to liability of cells.
Amniotic fluid: Room temperature.
Maternal Cell Contamination Specimen: Room temperature.
- Unacceptable Conditions
- Maternal specimen is recommended for proper test interpretation. Order Maternal Cell Contamination. 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 Cell Contamination Specimen: Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable
Characteristics: Sickle cell disease results in vascular occlusion and tissue ischemia, and acute or chronic organ dysfunction. Milder forms present with hemolytic anemia.
Incidence: Sickle cell affects 1 in 250-600 African-Americans. HbS causes 60 to 70% of sickle cell disease in the United States (1 in 2000 individuals). Carrier frequency of HbS is 8-10% in African-Americans. HbS is common in sub-Saharan Africa, India, and the Middle East. HbC is common in West Africa. HbE is common in Southeast Asia.
Inheritance: Autosomal recessive.
Cause: Beta globin gene (HbB) missence mutations. The three detected mutations, HbS, HbC, and HbE, have one amino acid change in the beta globin chain. While HbS and HbC result in abnormal beta chain structure, the HbE mutation affects splicing efficiency, resulting in decreased amounts of beta chain.
Mutations Tested: c.19G>A (HbC), c.20A>T (HbS), c.79G>A (HbE).
Clinical Sensitivity: Greater than 70% for sickle cell disease; other hemoglobinopathies vary depending upon patient's ethnicity.
Methodology: PCR and fluorescence resonance energy transfer.
Analytic Sensitivity: Greater than 99%.
Limitations: Mutations other than c.19G>A (HbC), c.20A>T (HbS), c.79G>A (HbE) will not be detected. Diagnostic errors can occur due to rare sequence variations.
For quality assurance purposes, ARUP Laboratories will confirm the above result at no charge following delivery. Order Confirmation of Fetal Testing and include a copy of the original fetal report (or the mother's name and date of birth) with the test submission. Please contact an ARUP genetic counselor at (800) 242-2787 extension 2141 prior to specimen submission.
This test is performed pursuant to an agreement with Roche Molecular Systems, Inc.
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||31208-2|
|0050612||Maternal Contam Study, Maternal Spec||31208-2|
|0051423||Beta Globin Gene Allele 1||55241-4|
|0051424||Beta Globin Gene Allele 2||55242-2|
|0051425||Beta Globin (HbS,C,E) Interpretation||21689-5|
|0051427||Beta Globin (HbS, C, E) Fetal Specimen|
- Fetal HbS, HbC, HbE mutation testing