Test Catalog

Test Id : WBSEQ

Beta Globin Gene Sequencing, Varies

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

Diagnosis of beta thalassemia intermedia or major

 

Identification of a specific beta thalassemia sequence variant (ie, unusually severe beta thalassemia trait)

 

Evaluation of an abnormal hemoglobin electrophoresis identifying a rare beta-globin variant

 

Evaluation of chronic hemolytic anemia of unknown etiology

 

Evaluation of hereditary erythrocytosis with left-shifted p50 oxygen dissociation results

 

Preconception screening when there is a concern for a beta-hemoglobin disorder based on family history

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

Beta-globin gene (HBB) sequencing can be used to identify hemoglobin variants and the most common beta thalassemia sequence variants, including beta plus and beta zero thalassemias. It also identifies hyper-unstable hemoglobin variants and dominant beta thalassemia sequence variants, as well as other hemoglobin variants that cannot be identified by protein methods. Some hemoglobin disorders will not be detected by beta-globin gene sequencing, such as large deletional alterations and crossover events. As such, the results of this test should always be interpreted within the context of the protein studies and red blood cell indices.

Highlights

This is a second-tier evaluation of beta thalassemia minor, intermedia, and major, as well as beta-globin variant identification.

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

A hemoglobin electrophoresis evaluation (HBEL1 / Hemoglobin Electrophoresis Evaluation, Blood) is always indicated prior to beta-globin gene sequencing because these conditions can be complex and protein data allows accurate and rapid classification of the patient phenotype.

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)/Sanger Sequencing

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

Beta Globin Gene Sequencing, B

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

Beta Globin

Beta Thalassemia

Beta-thalassemia

Thalassemia: Beta

Hemoglobin Variant: Beta

HBB

Hemoglobin S

Hb S

Hemoglobin C

Hb C

Hemoglobin E

Hb E

Beta Globin Sequencing

Beta Hemoglobin

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

A hemoglobin electrophoresis evaluation (HBEL1 / Hemoglobin Electrophoresis Evaluation, Blood) is always indicated prior to beta-globin gene sequencing because these conditions can be complex and protein data allows accurate and rapid classification of the patient phenotype.

Specimen Type
Describes the specimen type validated for testing

Varies

Ordering Guidance

For first-tier testing for beta thalassemia, order THEV1 / Thalassemia and Hemoglobinopathy Evaluation, Blood and Serum.

 

For first-tier testing for beta-globin variant detection, order HBEL1 / Hemoglobin Electrophoresis Evaluation, Blood.

Necessary Information

1. Patient's age is required.

2. Include recent transfusion information.

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Specimen Type: Peripheral blood

Container/Tube:

Preferred: Lavender top (EDTA)

Acceptable: Yellow top (ACD), green top (sodium heparin)

Specimen Volume: 4 mL

Collection Instructions:

1. Invert several times to mix blood.

2. Send specimen in the original tube.

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:

1. Label specimen as extracted DNA and source of specimen

2. Provide volume and concentration of the DNA

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

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

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. If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:

Metabolic Hematology Patient Information (T810)

Benign Hematology Test Request (T755)

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

Blood: 1 mL

Extracted DNA: 50 mcL at 50 ng/mcL concentration

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Moderately to severely clotted Reject

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Varies Varies (preferred)

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

Diagnosis of beta thalassemia intermedia or major

 

Identification of a specific beta thalassemia sequence variant (ie, unusually severe beta thalassemia trait)

 

Evaluation of an abnormal hemoglobin electrophoresis identifying a rare beta-globin variant

 

Evaluation of chronic hemolytic anemia of unknown etiology

 

Evaluation of hereditary erythrocytosis with left-shifted p50 oxygen dissociation results

 

Preconception screening when there is a concern for a beta-hemoglobin disorder based on family history

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

Beta-globin gene (HBB) sequencing can be used to identify hemoglobin variants and the most common beta thalassemia sequence variants, including beta plus and beta zero thalassemias. It also identifies hyper-unstable hemoglobin variants and dominant beta thalassemia sequence variants, as well as other hemoglobin variants that cannot be identified by protein methods. Some hemoglobin disorders will not be detected by beta-globin gene sequencing, such as large deletional alterations and crossover events. As such, the results of this test should always be interpreted within the context of the protein studies and red blood cell indices.

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

A hemoglobin electrophoresis evaluation (HBEL1 / Hemoglobin Electrophoresis Evaluation, Blood) is always indicated prior to beta-globin gene sequencing because these conditions can be complex and protein data allows accurate and rapid classification of the patient phenotype.

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Beta-globin gene sequencing is useful in the evaluation of beta-globin chain variants and beta thalassemia. It detects almost all beta-globin variants and the most common beta thalassemia sequence variants, although prevalence is ethnicity dependent. Because these conditions are often complex, this test should always be interpreted in the context of protein studies, such as hemoglobin electrophoresis and red blood cell indices.

 

The majority of beta-globin chain variants are clinically and hematologically benign; however, some have important clinical consequences, such as erythrocytosis, cyanosis/hypoxia, chronic hemolysis, or unexplained microcytosis. Most of the common clinically significant hemoglobin (Hb) variants (ie, HbS, HbC, HbE, and others) are easily distinguished by hemoglobin electrophoresis and do not require molecular analysis. In addition, they are frequently found in complex hemoglobin disorders due to multiple genetic variants, and accurate classification requires sequencing data within the context of protein data. In some instances, beta-globin sequencing is necessary to identify or confirm the identity of rare variants, especially those associated with erythrocytosis and chronic hemolytic anemia. Rare hyper-unstable variants (also termed dominant beta thalassemia mutations) result in hemolytic anemia and do not create protein stable enough to be detectable by protein methods, including stability studies. They are not always associated with elevated HbA2 or microcytosis and, therefore, can be electrophoretically silent. These require a high degree of clinical suspicion as all electrophoretic testing as well as stability studies cannot exclude this condition.

 

Beta thalassemia is an autosomal recessive condition characterized by decreased or absent synthesis of beta-globin chains due to sequence variants in the beta-globin gene (HBB). No abnormal protein is present and diagnosis by electrophoresis relies on hemoglobin fraction percentage alterations (ie, HbA2 or HbF elevations).

 

Beta thalassemia can be split into 3 broad classes (categorized by clinical features):

1. Beta thalassemia trait (also called beta thalassemia minor and beta thalassemia carrier) (B[A]B[+] or B[A]B[0])

2. Beta thalassemia intermedia (B[+]B[+] or B[+]B[0])

3. Beta thalassemia major (B[+]B[0] or B[0]B[0])

 

Beta thalassemia trait is typically a harmless condition with varying degrees of microcytosis and hypochromia and sometimes mild anemia. Transfusions are not required. Beta thalassemia intermedia is a clinical distinction and is characterized by a more severe degree of anemia than beta thalassemia trait with few or intermittent transfusions required. Later in life, these individuals are at risk for iron overload even in the absence of chronic transfusion due to increased intestinal absorption of iron. Beta thalassemia major typically comes to medical attention early in life due to severe anemia, hepatosplenomegaly, and failure to thrive. Skeletal changes are also common due to expansion of the bone marrow. Without appropriate treatment these patients have a shortened lifespan.

 

The majority of beta thalassemia variations (>90%) are point alterations, small deletions, or insertions, which are detected by beta-globin gene sequencing. The remaining beta thalassemia sequence variants are either due to large genomic deletions of HBB or, very rarely, trans-acting beta thalassemia variations located outside of the beta-globin gene cluster. Some rare beta-chain variants can be clinically or electrophoretically indistinguishable from beta thalassemia and cannot be confirmed without molecular analysis.

Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

An interpretive report will be provided.

Interpretation
Provides information to assist in interpretation of the test results

The alteration will be provided with the classification, if known. Further interpretation requires correlation with protein studies and red blood cell indices.

Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

This assay will not detect large deletions or duplications within the beta globin gene. In addition, hybrid beta globin variants (ie, hemoglobin Lepore) will not be detected by this method. This method cannot distinguish between homozygous and compound heterozygous variants associated with large deletions. This method cannot distinguish between double substitution on single chromosome and a compound heterozygous state. Beta globin sequencing alone is not able to distinguish between alterations that are found in the same copy of the HBB gene (ie, variants that are "linked" or "in cis") and alterations found on different HBB gene copies (ie, are "in trans"). This limitation of sequencing may complicate diagnosis and has implications for inheritance and proper genetic counseling. To resolve these cases, molecular results must be correlated with electrophoretic and protein data, other laboratory findings, clinical findings, and family studies. Misinterpretation of results may occur if the information provided is inaccurate or incomplete.

 

Rare genetic alterations exist that could lead to false-negative or false-positive results. If results obtained do not match the clinical findings, additional testing should be considered.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Hoyer JD, Hoffman DR: The thalassemia and hemoglobinopathy syndromes. In: McClatchey KD, ed. Clinical Laboratory Medicine. 2nd ed. Lippincott Williams and Wilkins; 2002:866-895

2. Thein SL: The molecular basis of beta-thalassemia. Cold Spring Harb Perspect Med. 2013 May;1;3(5):a011700

3. Hoyer JD, Kroft, SH: Color Atlas of Hemoglobin Disorders: A Compendium Based on Proficiency Testing. CAP; 2003

4. Merchant S, Oliveira JL, Hoyer JD, Viswanatha DS: Molecular diagnosis in hematopathology. In: Goldblum J, ed. Hematopathology: A Volume in Foundations in Diagnostic Pathology Series. 2nd ed.  Volume Editor E Hsi. Churchill Livingstone; 2012

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

Method Description
Describes how the test is performed and provides a method-specific reference

Genomic DNA is extracted from whole blood. The HBB gene is amplified by polymerase chain reaction (PCR). The PCR product is then purified and sequenced in both directions using fluorescent dye-terminator chemistry. Sequencing products are separated on an automated sequencer and trace files analyzed for variations in all exons, introns with the exception of IVS-II-82 through IVS-II-650, the 5'UTR, the 3'UTR, and the promoter region. Results are correlated with routine studies to identify unusual beta globin variants.(Reddy PL, Bowie LJ: Sequence-based diagnosis of hemoglobinopathies in the clinical laboratory. Clin Lab Med. 1997;17[1]:85-96; Traeger-Synodinos J, Harteveld CL: Advances in technologies for screening and diagnosis of hemoglobinopathies. Biomarkers Med. 2014;8[1]:115-127)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information

No

Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday through Friday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

2 to 10 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

DNA 3 months

Performing Laboratory Location
Indicates the location of the laboratory that performs the test

Rochester

Fees
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

  • Authorized users can sign in to Test Prices for detailed fee information.
  • Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
  • Prospective clients should contact their Regional Manager. For assistance, contact Customer Service.

Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

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 US Food and Drug Administration.

CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.

81364-HBB (hemoglobin, beta) full sequence

LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
WBSEQ Beta Globin Gene Sequencing, B 79401-6
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
62128 Beta Globin Gene Sequencing, B 82939-0
43922 Interpretation 69047-9

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Create a PDF

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports