Test Id : WASEQ
Alpha Globin Gene Sequencing, Varies
Useful For
Suggests clinical disorders or settings where the test may be helpful
Diagnosing nondeletional alpha thalassemia
Testing for nondeletional alpha thalassemia in a symptomatic individual
Follow-up testing to an abnormal hemoglobin electrophoresis that identified an alpha-globin chain variant
Genetics Test Information
Provides information that may help with selection of the correct genetic test or proper submission of the test request
A hemoglobin electrophoresis evaluation (HBEL1 / Hemoglobin Electrophoresis Evaluation, Blood) is always indicated prior to alpha-globin gene sequencing because these conditions can be complex and protein data allows accurate and rapid classification of the patient phenotype.
Not the preferred first-tier molecular test for carrier screening or diagnosis of alpha thalassemia. This test is used to identify nondeletional alpha-thalassemia variants when there is a strong clinical suspicion and AGDD / Alpha Globin Cluster Locus Deletion/Duplication, Varies is negative. This test can also identify alpha-globin variants that can result in variable phenotypes, such as erythrocytosis, chronic hemolytic anemia, and many that are clinically benign.
Highlights
This test is a second-tier test in the evaluation of alpha-thalassemia carrier determination, hemoglobin H disease confirmation, and alpha-globin variant identification.
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.
Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test
Aliases
Lists additional common names for a test, as an aid in searching
Alpha Globin
Alpha Thalassemia
HBA1
HBA2
HB Barts
HB H Disease
Alpha-thalassemia
Hydrops Fetalis
Thalassemia, Alpha
Hemoglobin variant, Alpha
Alpha Globin Sequencing
Alpha Hemoglobin
Specimen Type
Describes the specimen type validated for testing
Varies
Ordering Guidance
For first tier testing for alpha thalassemia detection, order THEV1 / Thalassemia and Hemoglobinopathy Evaluation, Serum and Blood.
For first tier testing for an alpha-globin variant, order HBEL1 / Hemoglobin Electrophoresis Evaluation, Blood.
If genetic testing is desired, the first-tier genetic test assesses large deletional alpha-thalassemia alterations. Order AGDD / Alpha Globin Cluster Locus Deletion/Duplication, Varies.
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
Submit only 1 of the following specimens:
Specimen Type: Whole 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 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:
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 in Special Instructions:
-Informed Consent for Genetic Testing (T576)
-Informed Consent for Genetic Testing-Spanish (T826)
2. Metabolic Hematology Patient Information (T810)
3. If not ordering electronically, complete, print, and send Benign Hematology Test Request Form (T755) with the specimen
Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the testing laboratory. The minimum volume is sufficient for one attempt at testing.
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
| Gross hemolysis | OK |
| 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 | ||
Useful For
Suggests clinical disorders or settings where the test may be helpful
Diagnosing nondeletional alpha thalassemia
Testing for nondeletional alpha thalassemia in a symptomatic individual
Follow-up testing to an abnormal hemoglobin electrophoresis that identified an alpha-globin chain variant
Genetics Test Information
Provides information that may help with selection of the correct genetic test or proper submission of the test request
A hemoglobin electrophoresis evaluation (HBEL1 / Hemoglobin Electrophoresis Evaluation, Blood) is always indicated prior to alpha-globin gene sequencing because these conditions can be complex and protein data allows accurate and rapid classification of the patient phenotype.
Not the preferred first-tier molecular test for carrier screening or diagnosis of alpha thalassemia. This test is used to identify nondeletional alpha-thalassemia variants when there is a strong clinical suspicion and AGDD / Alpha Globin Cluster Locus Deletion/Duplication, Varies is negative. This test can also identify alpha-globin variants that can result in variable phenotypes, such as erythrocytosis, chronic hemolytic anemia, and many that are clinically benign.
Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Alpha-globin gene sequencing detects alpha-globin variants and nondeletional alpha-thalassemia variants.
Alpha thalassemia is the most common monogenic condition in the world. It is estimated that up to 5% of the world's population carries at least one alpha-thalassemia variant and, in the United States, approximately 30% of African Americans are thought to carry an alpha-thalassemia variant. Alpha-thalassemia variations are most common in individuals of Southeastern Asian, African, Mediterranean, Indian, and Middle Eastern descent, but they can be found in persons from any ethnic group.
Four alpha-globin genes are normally present, 2 copies on each chromosome 16. Alpha-thalassemia variants result in decreased alpha-globin chain production. In general, alpha thalassemia is characterized by hypochromic, microcytic anemia and varies clinically from asymptomatic (alpha-thalassemia silent carrier and alpha-thalassemia trait) to lethal hemolytic anemia (hemoglobin [Hb] Barts hydrops fetalis).
Large deletions of the alpha-globin genes account for approximately 90% of alpha-thalassemia alterations, and these variations will not be detected by alpha-globin gene sequencing. Other variants, such as point alterations or small deletions within the alpha-globin genes, account for most of the remaining 10% of alpha-thalassemia variations. These nondeletional subtypes can be detected by alpha-globin gene sequencing. The most common nondeletional alpha-thalassemia variant is Hb Constant Spring.
The majority of alpha-globin chain variants are clinically and hematologically benign however, some cause erythrocytosis and chronic hemolytic anemia. Hemoglobin electrophoresis may not be able to confirm their identity. In these instances, alpha-globin gene sequencing can be useful.
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
An interpretive report will be provided.
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 alpha-globin genes. Therefore, test results should be interpreted in the context of hemoglobin electrophoresis, clinical findings, family history, and other laboratory data. Misinterpretation of results may occur if the information provided is inaccurate or incomplete.
Rare genetic alterations (ie, polymorphisms) 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. Harteveld CL, Higgs DR: Alpha-thalassemia. Orphanet J Rare Dis. 2010;5:13
2. 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
3. Farashi S, Harteveld CL: Molecular basis of a-thalassemia. Blood Cells Mol Dis. 2018 May;70:43-53. doi: 10.1016/j.bcmd.2017.09.004
4. Henderson SJ, Timbs AT, McCarthy J, et al: Ten years of routine a- and B-globin gene sequencing in UK hemoglobinopathy referrals reveals 60 novel mutations. Hemoglobin. 2016;40(2):75-84. doi: 10.3109/03630269.2015.1113990
Method Description
Describes how the test is performed and provides a method-specific reference
Genomic DNA is extracted from whole blood. The HBA1 and HBA2 genes are 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 the trace files analyzed for variations in all exons, introns, and the polyadenylation site. Results are correlated with routine studies to identify unusual alpha 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]:119-131)
PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information
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.
Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location
Indicates the location of the laboratory that performs the test
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 account representative. 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. It 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.
CPT codes are provided by the performing laboratory.
81259-HBA1/HBA2; 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 |
|---|---|---|
| WASEQ | Alpha Globin Gene Sequencing, B | 87730-8 |
| 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.
|
|---|---|---|
| 43921 | Interpretation | 69047-9 |
| 61362 | Alpha Globin Gene Sequencing, B | 87730-8 |