α-Thalassemia, Fetal Analysis

This test is used for prenatal diagnosis for pregnancies at risk for alpha-thalassemia. This analysis includes seven common alpha-thalassemia deletions (a-3.7, a-4.2, SEA, MED, THAI, FIL, and alpha-(20.5)), as well as the Constant Spring variant and the HS-40 regulatory region.

Labcorp clients with eight-digit client account numbers should call 800-345-4363, and Labcorp Genetics & Women's Health clients with six-digit client/subclient account numbers should call 800-255-7357 to speak with a laboratory genetic coordinator before collecting specimens. In some circumstances, specimens from both parents and other family members may be required. All fetal specimens, including cord blood, must be accompanied by a maternal blood, PurFlock buccal swab kit or Oragene Dx 500 saliva kit for maternal cell contamination (MCC). A separate requisition should be submitted with the maternal specimen.

This test includes the following genes: HBA1, HBA2.

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.

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.

Maternal cell contamination analysis (MCC): analysis of short tandem repeat markers by multiplex fluorescent polymerase chain reaction (PCR) and capillary electrophoresis

Nagan, M, Faulkner NE, Curtis C, Schrijver I, MCC Guidelines Working Group of the Association for Molecular Pathology Clinical Practice Committee. Laboratory Guidelines for Detection, Interpretation, and Reporting of Maternal Cell Contamination in Prenatal Analyses. J Mol Diagn. 2011 Jan;13(1):7-11. PubMed 21227389

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