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Test Code WGSQR Gamma-Globin Full Gene Sequencing, Varies


Specimen Required


Only orderable as a reflex. For more information see:

-HAEVP / Hemolytic Anemia Evaluation

-HBELC / Hemoglobin Electrophoresis Cascade, Blood

-MEVP / Methemoglobinemia Evaluation

-REVE / Erythrocytosis Evaluation

THEVP / Thalassemia and Hemoglobinopathy Evaluation


Secondary ID

47960

Useful For

Evaluates for the following in an algorithmic process for the HAEVP / Hemolytic Anemia Evaluation; HBELC / Hemoglobin Electrophoresis Cascade, Blood; MEVP / Methemoglobinemia Evaluation; REVE / Erythrocytosis Evaluation; THEVP / Thalassemia and Hemoglobinopathy Evaluation:

-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)

Method Name

Only orderable as a reflex. For more information see:

-HAEVP / Hemolytic Anemia Evaluation

-HBELC / Hemoglobin Electrophoresis Cascade, Blood

-MEVP / Methemoglobinemia Evaluation

-REVE / Erythrocytosis Evaluation

THEVP / Thalassemia and Hemoglobinopathy Evaluation

Reporting Name

Gamma Globin Full Gene Sequencing

Specimen Type

Varies

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time
Varies Varies 30 days

Clinical Information

Hemoglobin (Hb) F is the dominant hemoglobin at birth but is gradually replaced by adult hemoglobin (Hb A) during the year after birth (normal value ≤1% of total hemoglobin after age 2). Increased Hb F levels may continue after the neonatal period and into adulthood for various reasons. Genetic causes include deletional and nondeletional forms of hereditary persistence of fetal hemoglobin (HPFH) and delta-beta-thalassemia mutations. Over 100 mutations have been described in the gamma genes and, if detectable, the protein expression will vary over time according to the overall Hb F expression. Gamma globin mutations can manifest either as a quantitative (gamma-thalassemia or nondeletional HPFH) or a qualitative (gamma variant) abnormality. Nondeletional HPFH mutations frequently modulate the expected severity of sickling disorders due to the inhibitory properties of Hb F on sickle formation. Many gamma chain variants are benign, although some, such as unstable, high- and low-oxygen affinity, or M hemoglobin variants, cause hemolytic anemia/hyperbilirubinemia, erythrocytosis, cyanosis, and methemoglobinemia, respectively. The percentages of gamma variants will vary according to if they are present on the HBG1 or HBG2 genes, as these genes are differentially expressed depending on the age of the patient. Symptoms due to gamma variants are expected to decrease along with the normal decrease in Hb F and, therefore, most resolve after the first 6 months of life.

Reference Values

Only orderable as a reflex. For more information see:

-HAEVP / Hemolytic Anemia Evaluation

-HBELC / Hemoglobin Electrophoresis Cascade, Blood

-MEVP / Methemoglobinemia Evaluation

-REVE / Erythrocytosis Evaluation

THEVP / Thalassemia and Hemoglobinopathy Evaluation

Interpretation

An interpretive report will be provided and will include specimen information, assay information, and whether the specimen was positive for any mutations in the gene. If positive, the mutation will be correlated with clinical significance, if known.

Clinical Reference

1. Crowley MA, Mollan TL, Abdulmalik OY, et al: A hemoglobin variant associated with neonatal cyanosis and anemia. N Engl J Med 2011;364:1837-1843

2. Cui J, Baysdorfer C, Azimi M, et al: Identification of three novel Hb F variants: Hb F-Hayward [Gy(NA1)Gly->Asp, GGT>GAT], Hb F-Chori-I [AyT16(A13)Gly->Asp, GGC>GAC] and Hb F-Chori-II [AyI29(B11)Gly->Glu, GGA>GAA]. Hemoglobin 2012;36:305-309

3. Akinsheye I, Alsultan A, Solovieff N, et al: Fetal hemoglobin in sickle cell anemia. Blood 2011;118:19-27

4. Disorders of Hemoglobin Genetics, Pathophysiology, and Clinical Management. Second edition. Edited by M Steinberg, B Forget, D Higgs, D Weatherall. New York, Cambridge University Press, 2009

5. Molecular Hematology. Third edition. Edited by D Provan, J Gribben. Malden, Massachusetts, Blackwell Publishing, 2010

6. Color Atlas of Hemoglobin Disorders: A Compendium Based on Proficiency Testing. Edited by JD Hoyer, SH Kroft. Northfield, IL. College of American Pathologists, 2003

7. Merchant S, Oliveira JL, Hoyer JD, Viswanatha DS: Chapter 24. Molecular diagnosis in hematopathology. In Hematopathology: A Volume in the Series: Foundations in Diagnostic Pathology. Second edition. Edited by J Goldblum. E Hsi. Churchill Livingstone. 2012

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
WGSQR Gamma Globin Full Gene Sequencing In Process

 

Result ID Test Result Name Result LOINC Value
47950 Gamma Globin Gene Sequencing Result In Process
47951 Gamma Globin Interpretation In Process