Alpha Thalassemia DNA Screen

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General Information

Lab Name
Alpha Thalassemia DNA Screen
Lab Code
ATHAL
Epic Ordering
Alpha Thalassemia DNA Screen
Description

DNA analysis provides definitive diagnosis of alpha-thalassemia trait and determines whether a patient has a one-gene deletion or a two-gene cis deletion. In the setting of reproductive counselling, identification of a two-gene cis deletion in both prospective parents indicates they are at risk of having a fetus with hemoglobin Bart hydrops fetalis, which is almost always fatal before birth.

The alpha-globin gene cluster at chromosome band 16p13 consists of two adjacent alpha-globin genes (HBA1 and HBA2) on each chromosome for a total of four genes. This assay detects six of the most common deletions found in patients with alpha-thalassemia (Tan et al. 2001). In two of these common deletions, the 3.7 kb deletion type and the 4.2 kb deletion type, only one of the four alpha globin genes is deleted. In the other four common deletions, known as the SEA (Southeast Asian) deletion type, FIL (Filipino) deletion type, the THAI (Thailand) deletion type, and the MED (Mediterranean) deletion type, two adjacent (cis) alpha-globin genes are deleted (both from the same chromosome). About 95% of all alpha-thalassemia is due to gene deletions that are detected by this test (detection rates may vary in specific populations).

Indications for testing include:

  • Detection of prospective parents at risk for a pregnancy with Hb Bart hydrops fetalis
  • Prenatal diagnosis of alpha-thalassemia in pregnancies at risk (Note: If clinically indicated, prenatal test results can be confirmed at no charge after birth or termination of pregnancy.)
  • Differential diagnosis of microcytic anemia

NOTE: For outside patients please provide additional clinical and family history. Please include the following available laboratory data: CBC, Hb electrophoresis, and iron studies.

References
  • Harteveld CL and Higgs DR. Alpha-thalassaemia. Orphanet J Rare Dis 2010, 5:13. 20507641
  • Chui DH, Fucharoen S, and Chan V. Hemoglobin H disease: not necessarily a benign disorder. Blood 2003, 101:791-800. 12393486
  • Skogerboe KJ, et al. Screening for alpha-thalassemia. Correlation of hemoglobin H inclusion bodies with DNA-determined genotype. Arch Pathol Lab Med 1992, 116:1012-8. 1329692
Forms & Requisitions

Genetics Requisition

Synonyms
Alpha thalassemia, Globin Gene, Hemoglobin Bart's, Hydrops Fetalis
Components

Interpretation

Method

The target deletions on the genes HBA1 and HBA2 are evaluated using PCR (Polymerase Chain Reaction) with agarose gel electrophoresis. This test was developed and its performance characteristics determined by the Department of Laboratory Medicine at the University of Washington.

Reference Range
See individual components
Ref. Range Notes

No deletion mutation detected.

References
  • Harteveld CL and Higgs DR. Alpha-thalassaemia. Orphanet J Rare Dis 2010, 5:13. 20507641
  • Chui DH, Fucharoen S, and Chan V. Hemoglobin H disease: not necessarily a benign disorder. Blood 2003, 101:791-800. 12393486
  • Skogerboe KJ, et al. Screening for alpha-thalassemia. Correlation of hemoglobin H inclusion bodies with DNA-determined genotype. Arch Pathol Lab Med 1992, 116:1012-8. 1329692
Guidelines

Ordering & Collection

Specimen Type
Blood, amniocytes, chorionic villus tissue or cultured cells
Collection

Blood

  • Adult: 5 mL LAVENDER TOP tube
  • Child: 2 mL LAVENDER TOP tube
  • Also acceptable: YELLOW TOP (ACD) tube
  • Unacceptable: Heparin green top tubes

Amniocytes or Cultured Chorionic Villus Cells

  • Two (2) T23 or
  • One (1) T75 flask (minimum 1-T25 flask)

Chorionic Villi and/or Tissue

In sterile tube or culture media, at least 5 mg tissue. Prenatal testing requires concomitant testing for maternal cell contamination (see Online Test Guide, Lab Mnemonic Maternal Cell Contamination [MCC] for ordering and specimen requirements)

NOTE: For outside patients please provide additional clinical and family history. Please include the following available laboratory data: CBC, Hb electrophoresis, and iron studies.

Forms & Requisitions

Genetics Requisition

Handling Instructions

Ship whole blood at ambient temperature for receipt within 1 week of specimen collection. For cultured amniocytes or chorionic villus cells and for CVS or other tissue, transport and store at room temperature within 24 hours of obtaining CV or removing cultured cells from incubator.

Quantity
requested: Entire specimen
minimum: Blood: 1 mL. Amniocytes, cultured chorionic villus cells, chorionic villi or tissue: as above.

Processing

Processing

Processing: Please notify genetics about amniocytes, cultured chorionic villus cells, chorionic villi or tissue.

  • Blood: Refrigerate whole blood up to 1 week
  • Amniocytes & cultured CVS cells: hold flasks at room temperature
  • Chorionic villi and/or tissue: hold at room temperature

Performance

LIS Dept Code
Genetics (GEN)
Performing Location(s)
UW-MT Genetics

Attention: Genetics Lab
Clinical lab, Room NW220
University of Washington Medical Center
1959 NE Pacific Street
Seattle, WA 98195

Tel: 206-598–6429 M–F (7:30 AM–4:00 PM)
Fax: 206-598–0304
Lab email: genelab@uw.edu

Tel (EXOME only): 206-543-0459

Manager

Rebecca Gaulin, rgaulin@uw.edu

Genetic Counselors

Angela Jacobson, MS, LGC agibson@uw.edu
Sarah Paolucci, MA, MS, LGC, spaolucc@uw.edu
Jenna Huey, MS, LGC, jlhuey@uw.edu
Sandra Coe, MS,LGC, scoe20@uw.edu
Dru Leistritz, MS, LGC, dru2@uw.edu (EXOME testing only)

Variant Review Scientist

Ankita Jhuraney, PhD

Faculty

Colin C. Pritchard, MD, PhD
Brian H. Shirts, MD, PhD
Christina Lockwood, PhD, DABCC
Stephen Salipante, MD, PhD
Eric Konnick, MD, MS
Niklas Krumm, MD,PhD
Vera Paulson, MD, PhD
Jillian Buchan, PhD, FACMG

Frequency
Performed weekly. Results within 2 weeks.
Available STAT?
No

Billing & Coding

CPT codes
81257
Billing Comments

For pricing information, contact Client Support Services 206-520-4600 or 800-713-5198.

LOINC
55234-9