Test Details
Methodology
Analysis of the alpha-globin (HBA) gene cluster is performed by polymerase chain reaction (PCR) and multiplex ligation-dependent probe amplification (MLPA). Alpha-globin variants included in the analysis are the Constant Spring non-deletion variant and the following deletions: -alpha3.7, -alpha4.2, --alpha20.5, --SEA, --FIL, --THAI, --MED, and the HS-40 regulatory region.
Result Turnaround Time
9 - 12 days; in some cases, additional time may be required for confirmatory or reflex tests
Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.
Test Includes
This test includes the following genes: HBA1, HBA2.
Use
This test is used for diagnostic or carrier testing for alpha-thalassemia.
Special Instructions
To test fetal specimens, including cord blood, order α-Thalassemia, Fetal Analysis [484293].
Limitations
Technologies used do not detect germline mosaicism and do not rule out the presence of large chromosomal aberrations including rearrangements and gene fusions, or variants in regions or genes not included in this test, or possible inter/intragenic interactions between variants or repeat expansions. Variant classification and/or interpretation may change with time if more information becomes available. False positive or false negative results may occur for reasons that include: rare genetic variants, sex chromosome abnormalities, pseudogene interference, blood transfusions, bone marrow transplantation, somatic or tissue-specific mosaicism, mislabeled samples or erroneous representation of family relationships.
This test was developed and its performance characteristics determined by Labcorp. It has not been cleared or approved by the Food and Drug Administration.
Specimen Requirements
Specimen
Whole blood or PurFlock buccal swab kit
Volume
7 mL whole blood or PurFlock buccal swab kit
Minimum Volume
3 mL whole blood or PurFlock buccal swab kit
Container
Lavender-top (EDTA) tube or yellow-top (ACD-A) tube or PurFlock buccal swab kit
Collection Instructions
Standard phlebotomy
Stability Requirements
| Temperature | Period |
|---|---|
| Room temperature | Whole blood: 14 days; buccal: 60 days |
| Refrigerated | Whole blood: 30 days |
Storage Instructions
Maintain specimen at room temperature or refrigerate at 4°C. Do not freeze.
Causes for Rejection
Frozen or hemolyzed specimen; quantity not sufficient for analysis; improper container; one buccal swab; wet buccal swab
References
Tamary H, Dgany O. Alpha-Thalassemia. Adam MP, Feldman J, Mirzaa GM, Pagon RA, Wallace SE, Amemiya A, editors. In: GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993. 2005 Nov 1 [updated 2024 May 23]. PubMed 20301608