Alpha Thalassemia DNA Screen
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
- Synonyms
- Alpha thalassemia, Globin Gene, Hemoglobin Bart's, Hydrops Fetalis
- Components
-
Code Name ATRES Alpha Thalassemia Results ATCLIN Alpha Thalassemia Clin Info ATINT Alpha Thal Interpretation ATINFO Alpha Thalassemia Information
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, Fetal [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
- 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
- Transport 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 98195Tel: 206-598–6429 M–F (7:30 AM–4:00 PM)
Fax: 206-598–0304
Lab email: genelab@uw.eduTel (EXOME only): 206-543-0459
Manager
Joe Bernal, jbernal@uw.edu
Genetic Counselors
Angela Jacobson, MS, LGC agibson@uw.edu
Sandra Coe, MS,LGC, scoe20@uw.edu
Dru Leistritz, MS, LGC, dru2@uw.edu (EXOME testing only)
Daniel W. Serber, PhD, MS, LCGC, dwserber@uw.eduVariant Review Scientist
Ankita Jhuraney, PhD
Sarah Paolucci, MA, MS, LGC, spaolucc@uw.edu
Catherine A. Darcey, MScFaculty
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
- Billing Comments
For pricing information, contact Client Support Services 206-520-4600 or 800-713-5198.
- LOINC
- 55234-9