Test Catalog

Test ID: WGSEQ    
Gamma Globin Full Gene Sequencing, Varies

Useful For Suggests clinical disorders or settings where the test may be helpful

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 Provides information that may help with selection of the correct genetic test or proper submission of the test request

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

Special Instructions Library of PDFs including pertinent information and forms related to the test

Method Name A short description of the method used to perform the test

Polymerase Chain Reaction (PCR) Amplification/Sanger Sequence Analysis

NY State Available Indicates the status of NY State approval and if the test is orderable for NY State clients.

Yes

Reporting Name Lists a shorter or abbreviated version of the Published Name for a test

Gamma Globin Full Gene Sequencing

Aliases Lists additional common names for a test, as an aid in searching

HBG1
HBG2
HBGA
HBGG
Gamma hemoglobin
Agamma
Ggamma
Hereditary persistence of fetal hemoglobin