Alpha Globin Gene Analysis

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 the six most common deletions found in individuals with alpha thalassemia (alpha-3.7, alpha-4.2, SEA [Southeast Asian], FIL [Filipino], THAI [Thailand], and MED [Mediterranean]). Approximately 95% of all alpha-thalassemia is due to deletions detectable by this test (detection rates may vary by ethnicity).

Genetics & Solid Tumor Clinical Request Form

In most instances, this is performed as a first-tier test when evaluating for alpha thalassemia. If testing for alpha-globin sequencing is indicated, order “Alpha Hemoglobin DNA Sequence”. To order testing for a relative of an individual with a known alpha-globin sequence variant, order “Alpha Hemoglobin Sequencing, Relative”.

Indications for Testing

• Investigation into microcytic anemia.
• Carrier testing for an individual with or without a family history of alpha thalassemia.
• Reproductive risk assessment for an individual whose reproductive partner is a known alpha thalassemia carrier.
• Evaluation for a clinical suspicion of alpha thalassemia.
• Prenatal diagnosis of alpha thalassemia in at-risk pregnancies when the familial mutations are detectable by this assay.
• Follow-up for hydrops fetalis.

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

This assay detects the six most common deletions found in individuals with alpha thalassemia (alpha-3.7, alpha-4.2, SEA [Southeast Asian], FIL [Filipino], THAI [Thailand], and MED [Mediterranean]). These target deletions on the HBA1 and HBA2 genes are evaluated using PCR (Polymerase Chain Reaction) with agarose gel electrophoresis. Other variants in the HBA1 and HBA2 genes (e.g., hemoglobin Constant Spring, alpha-thalassemia Saudi) are not detectable by this assay.

This test was developed and its performance characteristics were determined by the University of Washington Department of Laboratory Medicine and Pathology. It has not been cleared or approved by the US Food and Drug Administration. This laboratory is certified under the Clinical Laboratory Improvement Amendments (CLIA) as qualified to perform high-complexity clinical laboratory testing. This test is used for clinical purposes. It should not be regarded as investigational or for research.

Acceptable:

1. Whole blood:5 mL lavender top (EDTA) tube or yellow (ACD) top tube or 2 mL microtainer lavender top tube
   
   
2. Extracted DNA from blood, chorionic villi, and amniocytes: 500 ng (concentration >10 ng/uL)
   
   
3. Cultured amniocytes/chorionic villi: MCC is required for testing fetal samples. See MCC OLTG.
   
   
4. Also acceptable, but requires the Genetics Director's approval and a backup culture. Direct chorionic villi and/or TISSUE: Send 20mg of tissue in a sterile tube or RPMI culture media
   
   *NOTE: If a fetal sample (cultured amniocytes or chorionic villi) was received, add MCC to the order. Prenatal testing requires concomitant testing for maternal cell contamination (see Online Test Guide, MCC for ordering and specimen requirements). See Special Instructions.

Unacceptable: Heparin green top tubes, buccal swab

SPS specimen handling:

1. Whole blood sample: store in the refrigerator
   
   
2. Cultured amniocytes/chorionic villi: store at room temperature. Call the Genetics lab upon receipt (206)598-7021.
   
   
3. Extracted DNA: store in the refrigerator

If fetal tissue (cultured amniocytes or chorionic villi) was received for prenatal testing, consultation with the laboratory is required. Please notify the Genetics lab about prenatal studies via email at geneticshelp@uw.edu or call 206-598-7021.

For clients outside of UW, please include the most recent CBC and Hb electrophoresis result/s (if available), and/or any relevant clinical history.