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Alpha-Thalassemia 7 Deletions (8000101333)
Test Mnemonic:


Specimen Requirements:

Lavender(EDTA), Pink(K2EDTA), Yellow(ACD Solution A or B), white blood cells

Minimum Volume:

1 ml whole blood



Specimen Preparation:

No processing required.


Ambient: 72 hours; Refrigerated: 2 weeks; Frozen: 1 month

Causes for Rejection:

Incomplete and/or incorrect sample identification, hemolyzed samples.

Reference Range:


Turnaround Time:

10 days


Polymerase chain reaction (GAP-PCR) and gel electrophoresis


Molecular Diagnostics Laboratory


Alpha Thalassemia; Thalassemia; Alpha Globin gene deletion; HBA1; HBA2; Alpha globin gene analysis

Clinical Indication:

Genetic test for confirmation of suspected alpha-thalassemia

CPT 4 Code:



Background Information for Alpha-Thalassemia (HBA1 and HBA2) 7 Deletions:


Alpha-thalassemia silent carrier: Mutation of a single alpha globin gene (-α/αα); asymptomatic, no red cell abnormality.

Alpha-thalassemia trait: Mutation of two alpha globin genes in cis (--/αα) or in trans (-α/-α); asymptomatic, mild microcytic anemia possible.

Hemoglobin H (HbH) disease: Mutation of three alpha globin genes (--/-α); hemolysis with Heinz bodies, moderate anemia, and splenomegaly.

Hemoglobin Bart hydrops fetalis (Hb Bart) syndrome: Mutation of four alpha globin genes (--/--); lethal in fetal or early neonatal period without transfusions.

Incidence: Carrier frequency in Mediterranean (1:30-50), Middle Eastern, Southeast Asian (1:20), African, African-American (1:3).

Inheritance: Autosomal recessive.

Cause: Mutations in the alpha globin gene cluster; 95 percent are deletions.

Mutations Tested: -α3.7,-α4.2,-(α)20.5,--SEA,--MED,--FIL,--THAI

Clinical Sensitivity: Varies by ethnicity, may be as high as 90 percent.

Methodology: Polymerase chain reaction (GAP-PCR) and gel electrophoresis

Analytical Sensitivity and Specificity: 99 percent.

Limitations: Rare alpha globin gene deletions, non-deletion mutations including gene duplications, and mutations of the regulatory region will not be detected. Diagnostic errors can occur due to rare sequence variations.


OMIM numbers: alpha-thalassemia (604131), HBA1 (141800), HBA2 (141850).



Counseling and informed consent are recommended for genetic testing. Consent form are available online.

When ordering tests for which Medicare or Medicaid reimbursement will be sought, physicians should only order tests that are medically necessary for the diagnosis or treatment of the patient. Components of the organ or disease panels may be ordered individually. The diagnostic information must substantiate all tests ordered and must be in the form of an ICD-10 code or its verbal equivalent.
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