| Alpha-Thalassemia Deletion/Duplication (8000101334) | |
|---|---|
| Test Mnemonic: | ALPHA THAL MLPA |
| Test Mnemonic: | Alpha Thalassemia; Thalassemia; HBA1; HBA2; Alpha globin gene deletion; Alpha globin gene duplication; Alpha globin gene mutation; Alpha globin gene analysis |
| Specimen Requirements: | 10 days |
| Specimen Requirements: | Multiplex ligation-dependent probe amplification (MLPA) of the alpha globin gene cluster (HBZ, HBM, HBA2, HBA1, HBQ1) and its HS-40 regulatory region |
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Background Information for Alpha-Thalassemia Deletions/Duplications: Characteristics: Alpha-thalassemia silent carrier: Mutation of a single alpha globin gene (-α/αα); asymptomatic, no red cell abnormality. Alpha-thalassemia trait: Mutation of two alpha globin genes in cis (--/αα) or in trans (-α/-α); asymptomatic, mild microcytic anemia possible. Hemoglobin H (HbH) disease: Mutation of three alpha globin genes (--/-α); hemolysis with Heinz bodies, moderate anemia, and splenomegaly. Hemoglobin Bart hydrops fetalis (Hb Bart) syndrome: Mutation of four alpha globin genes (--/--); lethal in fetal or early neonatal period without transfusions.
Incidence: Carrier frequency in Mediterranean (1:30-50), Middle Eastern, Southeast Asian (1:20), African, African-American (1:3).
Inheritance: Autosomal recessive.
Cause: Mutations in the alpha globin gene cluster; ~85 percent are deletions. Mutations Tested: Deletions/duplications in the alpha-globin gene cluster and the Hb Constant Spring mutation.
Clinical Sensitivity: Varies by ethnicity, may be as high as 85 percent.
Methodology: Multiplex ligation-dependent probe amplification (MLPA) of the alpha globin gene cluster (HBZ, HBM, HBA2, HBA1, HBQ1) and its HS-40 regulatory region
Analytical Sensitivity and Specificity: 99 percent.
Limitations: Specific breakpoints of large deletions/duplications will not be determined; therefore, it may not be possible to distinguish mutations of similar size. This assay does not assess for non-deletional/duplicational mutations (eg., missense, nonsense, and splice site variants) within the coding or regulatory regions of the alpha globin cluster genes. Individuals carrying both a deletion and duplication within the alpha globin gene cluster may appear to have a normal number of alpha globin gene copies. Rare syndromic or acquired forms of alpha thalassemia associated with ATRX mutations will not be detected. Diagnostic errors can occur due to rare sequence variations. References: OMIM numbers: alpha-thalassemia (604131), HBA1 (141800), HBA2 (141850). Alpha-Thalassemia GeneReviews: Alpha-Thalassemia - GeneReviews® - NCBI Bookshelf (nih.gov)
Counseling and informed consent are recommended for genetic testing. Consent form is available online.
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| Synonyms: | Lavender(EDTA), Pink(K2EDTA), Yellow(ACD Solution A or B), white blood cells |
| Synonyms: | The assay is used for post-natal diagnostic testing for confirmation of suspected alpha-thalassemia or alpha-thalassemia trait indicated by clinical and/or hematologic findings. |
| Clinical Indication: | Negative |
| Patient Preparation : | 81404 |
| When ordering tests for which Medicare or Medicaid reimbursement will be sought, physicians should only order tests that are medically necessary for the diagnosis or treatment of the patient. Components of the organ or disease panels may be ordered individually. The diagnostic information must substantiate all tests ordered and must be in the form of an ICD-10 code or its verbal equivalent. | |