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Alpha Globin Genotype, Alpha Thal, Alpha Thalassemia

Alpha Globin Genotype, Alpha Thal, Alpha Thalassemia

Test Codes

Beaker: XMISC

Department

Send Outs

Instructions

This test is not included in the Beaumont Laboratory testing formulary; however, the Laboratory can facilitate specimen collection.

• This test is usually performed after hemoglobin electrophoresis and measurement of HbA₂ to rule out beta-thalassemia.
  

• This test will be billed to the patient's insurance. If not covered by insurance, the patient is responsible for the full cost of testing.

• Order test as a Miscellaneous Send Out (XMISC).

• Please call the Send Outs Laboratory before collecting an amniotic fluid specimen. All amniotic fluid specimens must be accompanied by a maternal blood specimen. This is necessary for maternal cell contamination testing. Obtain specimen during 14th – 17th week of gestation.

• After hours collection: Specimens may be drawn and ordered. 

Specimen Collection Criteria

Blood: Two (2) Lavender-top EDTA tube. (Minimum: 3.0 mL)

Rejection Criteria

Specimens not collected or processed as indicated.

In-Lab Processing

Maintain blood specimens at room temperature (20-26°C or 68-78.8°F) or amniotic fluid specimens refrigerated (2-8°C or 36-46°F) until transport.

Transport: 7.0 mL whole blood, at room temperature (20-26°C or 68-78.8°F), or 10.0 mL amniotic fluid, refrigerated (2-8°C or 36-46°F). (Minimum: 3.0 mL whole blood or 5.0 mL amniotic fluid.) 

Laboratory

Sent to LabCorp Integrated Genetic, Westborough, MA.

Performed

Results available in 10-14 days.

Reference Range

By report.

Test Methodology

Dosage Analysis by Polymerase Chain Reaction (PCR)/Multiplex Ligation-Dependent Probe Amplification (MLPA)/Luminex Technology.

Interpretation

By report.

Hemoglobin electrophoresis should usually be done prior to this test to exclude other diagnoses or to identify non-deletion types of alpha-thalassemia.

This test is not useful for diagnosis / confirmation of beta-thalassemia or hemoglobinopathies.

Clinical Disease

Alpha-thalassemia occurs in all ethnic groups but is especially common in African Americans (30%) and in Southeast Asians (at least 25%). It is also found frequently in individuals of Mid-Eastern and Indian ancestry. While deletion type of alpha-thalassemia is much more common, both non-deletion type and deletion type have been described in each affected population.

Alpha-thalassemia is caused by decreased synthesis of alpha-globin chains. Four alpha-globin genes are normally present (two on each chromosome 16). One, two, three, or four alpha-globin genes may be deleted or contain mutations in patients with alpha-thalassemia, with more than 30 alpha-haplotypes having been described. Phenotypically, these result in four categories of disease expression:

1. Deletion of one alpha-chain results in a normal phenotype (i.e., no CBC abnormalities). 
2. Alpha-thalassemia minor, with mild hematologic changes, but no major clinical difficulties, occurs with deletion of two alpha genes. 
3. Hemoglobin H disease, which is extremely variable but usually includes anemia due to hemolysis, jaundice, and hepatosplenomegaly (deletion of three alpha genes) 
4. Hydrops fetalis with deletion of all four alpha-globin genes variably results in utero demise.

CPT Codes

81257

Contacts

Last Updated

7/21/2024