Tests Added
0 items - $0
Menu

α-Thalassemia, DNA Analysis

Test Number: 511172 CPT: 81257
Related Information
Specimen Whole blood, amniotic fluid, chorionic villus sample (CVS) (Submission of maternal blood is required for fetal testing.)
Volume 7 mL whole blood, 10 mL amniotic fluid or 20 mg CVS
Minimum Volume 3 mL whole blood, 5 mL amniotic fluid or 10 mg CVS
Container Lavender-top (EDTA) tube, yellow-top (ACD) tube, sterile plastic conical tube, or two confluent T-25 flasks for fetal testing
Storage Instructions Maintain specimen at room temperature or refrigerate at 4°C.
Causes for Rejection Frozen specimen; hemolysis; quantity not sufficient for analysis; improper container; one buccal swab; wet buccal swab
Limitations This test is designed to detect copy-number changes in the α-globin gene cluster (deletions and duplications) of 28 different sequences in the HBA region. In addition, the assay detects the presence of the Constant Spring (Hb CS) mutation. Other point mutations, and variants in other genes, will not be detected by this assay. Molecular-based testing is highly accurate, but as in any laboratory test, rare diagnostic errors may occur.

Results for this test are for research purposes only by the assay’s manufacturer. The performance characteristics of this product have not been established. Results should not be used as a diagnostic procedure without confirmation of the diagnosis by another medically established diagnostic product or procedure.
Methodology Polymerase chain reaction (PCR) and multiplex ligation-dependent probe amplification (MLPA)
Additional Information α-Thalassemia (OMIM 141800) is the most common inherited disorder of hemoglobin (Hb) synthesis in the world, with gene frequencies varying between 1% and 98% throughout the tropics and subtropics. α-Thalassemia can occur in all ethnic groups but is more common in those of Southeast Asian descent. The American College of Obstetricians and Gynecologists recommends hemoglobinopathy screening for those of African, Southeast Asian, and Mediterranean descent. More than 95% of recognized α-thalassemia involves deletion of one or both α-globin genes from chromosome 16p13.3.

DNA analysis of the α-globin region (HBA1/HBA2, OMIM 141800/141850, 16pter-16p13.3) is performed by targeting 28 different sequences using multiplex ligation-dependent probe amplification (MLPA). This methodology detects genomic deletions and duplications involving this locus, including the seven most common types of α-Thalassemia deletions (α-3.7, α-4.2, SEA, MED1, MED2, THAI and FIL), as well the Constant Spring point mutation. DNA analysis of the common α-globin gene deletions performed by multiplex polymerase chain reaction (PCR) followed by agarose gel electrophoresis may, on occasion, be used for confirmatory purposes.
References Chong SS, Boehm CD, Higgs DR, Cutting GR. Single-tube multiplex-PCR screen for common deletional determinants of alpha-thalassemia. Blood. 2000 Jan 1; 95(1):360-362. PubMed 11017952

Chui DH, Waye JS. Hydrops fetalis caused by alpha-thalassemia: An emerging health care problem. Blood. 1998 Apr 1; 91(7): 2213-2222. PubMed 9516118

Fichera M, Spalletta A, Fiorenza F, et al. Molecular basis of alpha-thalassemia in Sicily. Hum Genet. 1997 Mar; 99(3):381-386. PubMed 9050927

Gallanello R, Cao A. Alpha-thalassemia. GeneReviews. 2008; http://www.genetests.org.

Liu JZ, Han H, Schouten JP, et al. Detection of alpha-thalassemia in China by using multiplex ligation-dependent probe amplification. Hemoglobin. 2008; 32(6):561-571. PubMed 19065334