Sign in →

Test Code WGSEQ Gamma-Globin Full Gene Sequencing, Varies


Necessary Information


A complete patient history is strongly encouraged.



Specimen Required


Submit only 1 of the following specimens:

 

Specimen Type: Whole 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 whole blood specimen in the original tube. Do not aliquot.

Specimen Stability Information: Refrigerate 30 days(preferred)/Ambient 14 days

 

Specimen Type: Extracted DNA from whole blood

Container/Tube: 1.5 to 2 mL tube

Specimen Volume: Entire specimen

Collection Instructions: Label specimen as extracted DNA from blood and provide indication of volume and concentration of the DNA

Specimen Stability Information: Frozen (preferred)/Refrigerate/Ambient


Forms

1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing-Spanish (T826)

2. Thalassemia/Hemoglobinopathy Patient Information (T358)

3. If not ordering electronically, complete, print, and send a Benign Hematology Test Request (T755) with the specimen.

Secondary ID

62982

Useful For

An adjunct in the interpretation of hemoglobin electrophoresis results

 

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

 

Assessment of unstable gamma chain variants when other tests for causes of hemolysis are unrevealing

Highlights

This test should 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

Specimen Minimum Volume

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

Specimen Stability Information

Specimen Type Temperature Time Special Container
Varies Varies

Reject Due To

Gross hemolysis OK
Bone marrow
Paraffin-embedded tissue
Frozen tissue
Paraffin-embedded bone marrow aspirate clot
Methanol-acetic acid (MAA)-fixed pellets
Moderately to severely clotted		 Reject

Clinical Information

Hemoglobin F (HbF) is the dominant hemoglobin at birth but is gradually replaced by adult hemoglobin (HbA) during the year after birth (normal value ≤1% of total hemoglobin after age 2 years). Increased HbF 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 variants. Over 100 genetic variants have been described in the gamma genes and, if detectable, the protein expression will vary over time according to the overall HbF expression. Gamma globin variants can manifest either as a quantitative (gamma thalassemia or nondeletional HPFH) or a qualitative (gamma variant) abnormality. Nondeletional HPFH alterations frequently modulate the expected severity of sickling disorders due to the inhibitory properties of HbF 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 HbF and therefore, most resolve after the first 6 months of life.

Reference Values

An interpretive report will be provided.

Interpretation

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

Method Description

Total genomic DNA is extracted from the sample, and the full gamma globin genes are amplified by polymerase chain reaction in separate reactions followed by Sanger sequencing. Review of the sequence data is performed using a combination of automated calls and manual inspection.(Unpublished Mayo method)

Day(s) Performed

Monday through Friday

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US 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 95795-1

 

Result ID Test Result Name Result LOINC Value
46952 Gamma Globin Gene Sequencing Result 50397-9
46953 Gamma Globin Interpretation 59466-3