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Test ID WGSEQ Gamma Globin Full Gene Sequencing, Varies

Useful For

An adjunct in the interpretation of hemoglobin electrophoresis results

 

Evaluation for suspected gamma variants or nondeletional hereditary persistence of fetal hemoglobin (HPFH)

 

Assess for unstable gamma chain variants (there are occasionally newborns who are jaundiced at birth, often requiring phototherapy, in which all other tests for causes of hemolysis are unrevealing)

Genetics Test Information

The beta-like hemoglobins include the epsilon, gamma, beta, and delta globins, whose genes are present on chromosome 11 in a linked cluster (ie, the beta globin complex). The gamma genes, HBG1 (Ay) and HBG2 (Gy), contain 3 exonic coding regions and 2 intronic intervening sequences (IVS). The genes produce gamma globin chains that form tetramers with alpha globin chains to create fetal hemoglobin (Hb F). HBG1 and HBG2 differ only in which amino acid is located at position 136 (alanine or glycine). The resultant proteins are named A-gamma and G-gamma, respectively. Although G-gamma is predominant at birth, this gradually reverses during the first year of life to become the normal adult G-gamma/A-gamma ratio, which is 2:3. Some people maintain an increased G-gamma:A-gamma ratio throughout life, which has been linked to certain polymorphisms in either gene. Additionally, some alterations in the promoter regions of the gamma globin genes are known to cause a form of hereditary persistence of fetal hemoglobin (HPFH), which is characterized by a significant but harmless elevation of Hb F into adulthood. If coinherited with sickle cell disease, HPFH has a strong modulating effect on the condition and appears to protect against some, but not all, of its complications. Some gamma mutations result in gamma chain hemoglobin variants, most of which are clinically insignificant; however, an incompletely studied subset causes neonatal disorders, such as hemolytic anemia, cyanosis, and methemoglobinemia.

Highlights

This test would be used as an adjunct to abnormal results detected by hemoglobin electrophoresis testing. It will assist with:

-Diagnosis of nondeletional hereditary persistence of fetal hemoglobin (HPFH)

-Identification of abnormal gamma chain variants (eg, unstable, high- or low-oxygen affinity, or M hemoglobins)

-Predicting the severity of a coinherited sickling disorder

-Evaluation of unexplained neonatal anemia, cyanosis, or hyperbilirubinemia

Method Name

Polymerase Chain Reaction (PCR) Amplification/Sanger Sequence Analysis

Reporting Name

Gamma Globin Full Gene Sequencing

Specimen Type

Varies


Shipping Instructions


Specimens must arrive within 30 days (720 hours) of collection.



Necessary Information


A complete patient history is strongly encouraged.



Specimen Required


Submit only 1 of the following specimens:

 

Specimen Type: Peripheral blood

Container/Tube:

Preferred: Lavender top (EDTA)

Acceptable: Yellow top (ACD)

Specimen Volume: 4 mL

Collection Instructions:

1. Invert several times to mix blood.

2. Send specimen in the original tube.

Specimen Stability: Refrigerate

 

Specimen Type: Extracted DNA from whole blood

Container/Tube: 1.5-2mL tube with indication of volume and concentration of DNA

Specimen Volume: Entire specimen

Collection Instructions:

1. Label specimen as extracted DNA from blood.

2. Write the DNA concentration on the specimen tube.

Specimen Stability: Frozen (preferred)/Refrigerate/Ambient


Specimen Minimum Volume

Blood: 1 mL; Extracted DNA: 50 mcL at 50 ng/mcL concentration

Specimen Stability Information

Specimen Type Temperature Time
Varies Varies 30 days

Reference Values

An interpretive report will be provided.

Day(s) and Time(s) Performed

Monday through Friday

Performing Laboratory

Mayo Medical Laboratories in Rochester

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

81479-Unlisted molecular

LOINC Code Information

Test ID Test Order Name Order LOINC Value
WGSEQ Gamma Globin Full Gene Sequencing In Process

 

Result ID Test Result Name Result LOINC Value
46952 Gamma Globin Gene Sequencing Result In Process
46953 Gamma Globin Interpretation In Process

Forms

1. Thalassemia/Hemoglobinopathy Patient Information (T358) in Special Instructions

2. New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (T576) in Special Instructions.