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HelpTest Code WBGDD Beta-Globin Gene Cluster, Deletion/Duplication, Varies
Additional Testing Requirements
Hemoglobin electrophoresis studies performed at Mayo Clinic Laboratories are highly recommended prior to this test to allow for more complete interpretation of results. See HBEL1 / Hemoglobin Electrophoresis Evaluation, Blood or THEV1 / Thalassemia and Hemoglobinopathy Evaluation, Blood and Serum.
Shipping Instructions
Specimens must arrive within 4 days (96 hours) of collection.
Necessary Information
Metabolic Hematology Patient Information (T810) is required. Send a completed form with the specimen. Document the reason for suspecting a large beta cluster locus deletion along with the hemoglobin F percentage and red blood cell indices for the patient.
Specimen Required
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 specimen in the original tube. Do not aliquot.
Specimen Stability Information: Refrigerated (preferred)/Ambient
Forms
1. Metabolic Hematology Patient Information (T810) is required.
2. 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)
Useful For
Determining the etiology of hereditary persistence of fetal hemoglobin (HPFH), delta-beta thalassemia, or other large deletions involving the beta-globin gene cluster
Diagnosing less common causes of beta thalassemia; these large deletional beta-thalassemia variants result in elevated hemoglobin (Hb) A2 and can have elevated HbF levels
Distinguishing homozygous HbS disease from a compound heterozygous HbS/large beta-globin cluster deletion disorder (ie, HbS/beta zero thalassemia, HbS/delta-beta zero thalassemia, HbS/HPFH, HbS/gamma-delta-beta thalassemia)
Diagnosing complex thalassemias where the beta-globin gene and one or more of the other genes in the beta-globin cluster have been deleted
Evaluating and classifying unexplained increased HbF percentages
Evaluating microcytic neonatal anemia
Evaluating unexplained long standing microcytosis in the setting of normal iron studies and negative alpha-thalassemia testing/normal Hb A2 percentages
Confirming gene fusion hemoglobin variants such as Hb Lepore and HbP-Nilotic
Confirming homozygosity vs hemizygosity of variants in the beta-like genes (HBB, HBD, HBG1, HBG2)
Investigating newborns with HbA levels greater than HbF on newborn screen in the absence of transfusion
This test is not useful for diagnosis or confirmation of alpha thalassemia, the most common beta thalassemias, or hemoglobin variants. It also does not detect non-deletional HPFH.
Genetics Test Information
This test can be used to identify a variety of conditions (see Highlights) that involve large deletions of the beta-globin gene cluster. These alterations will not be detected by DNA sequencing of the beta-globin gene.
Special Instructions
Method Name
Polymerase Chain Reaction (PCR) Analysis/Multiplex Ligation-Dependent Probe Amplification (MLPA)
Reporting Name
Beta Globin Gene Cluster, Del/Dup,VSpecimen Type
VariesSpecimen Minimum Volume
2 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Varies | Varies | ||
Reject Due To
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.Clinical Information
Large deletions involving the beta-globin cluster locus on chromosome 11 manifest with widely variable clinical phenotypes. Up to 10% of beta-thalassemia cases (dependent on ethnicity) are caused by large deletions in the beta-globin cluster. Other thalassemias including delta-beta thalassemia, gamma-delta-beta-thalassemia, epsilon gamma thalassemia, and epsilon-gamma-delta-beta-thalassemia, also result from functional loss of genes or the locus control region that controls globin gene expression. In addition, hereditary persistence of fetal hemoglobin (HPFH) is caused by deletions of variable size along the beta-globin cluster locus. Most, but not all, of the large deletion beta-globin cluster disorders are associated with variably elevated hemoglobin F percentages that persist after 2 years of age. In addition, many manifest in microcytosis. A notable exception is HPFH, which can have normal to minimal decreased mean corpuscular volume values. The correct classification of these deletions is important as they confer variable predicted protective phenotypes, and some are more protective than others when found in combination with a second beta-globin variant, such as HbS or beta thalassemia. In addition, identification of these deletions can explain lifelong microcytosis in the setting of normal iron studies and negative alpha thalassemia molecular results.
Interpretation
The alterations will be provided with the classification that fits the probe pattern, if known. Further interpretation requires correlation with protein studies and red blood cell indices.
Cautions
Non-deletional subtypes of beta thalassemia or hereditary persistence of fetal hemoglobin are not detected by this assay. In addition to disease-related probes, the multiplex ligation-dependent probe amplification technique utilizes probes localized to other chromosomal regions as the internal controls. In certain circumstances, these control probes may detect other diseases or conditions for which this test was not specifically intended. Results of the control probes are not normally reported. However, in cases where clinically relevant information is identified, the ordering physician will be informed of the result and provided with recommendations for any appropriate follow-up testing.
Method Description
Multiplex ligation-dependent probe amplification is utilized to test for the presence of large deletions or duplications in the beta-globin gene.(Unpublished Mayo method)
Day(s) Performed
Wednesday, Friday
Report Available
25 to 30 daysSpecimen Retention Time
Whole blood: 2 weeks; DNA: 3 monthsPerforming 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
81363-HBB (hemoglobin, beta, beta-globin) (e.g. beta thalassemia), duplication/deletion analysis
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| WBGDD | Beta Globin Gene Cluster, Del/Dup,V | 101634-4 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 620981 | Beta Globin Gene Cluster Del/Dup | 101634-4 |
| 620982 | Specimen | 31208-2 |
| 620983 | Reviewed by | 18771-6 |
| 620980 | Interpretation | 69047-9 |
Reference Values
An interpretive report will be provided