| Alpha-Thalassemia 7 Deletions (8000101333) | |
|---|---|
| Test Mnemonic: | ALPHA THAL PCR |
| Specimen Requirements: | Lavender(EDTA), Pink(K2EDTA), Yellow(ACD Solution A or B), white blood cells |
| Minimum Volume: | 1 ml whole blood |
| Storage/Transport: | Refrigerated |
| Specimen Preparation: | No processing required. |
| Stability: | Ambient: 72 hours; Refrigerated: 2 weeks; Frozen: 1 month |
| Causes for Rejection: | Incomplete and/or incorrect sample identification, hemolyzed samples. |
| Reference Range: | Negative |
| Turnaround Time: | 10 days |
| Methodology: | Polymerase chain reaction (GAP-PCR) and gel electrophoresis |
| Performed: | |
| Lab: | Molecular Diagnostics Laboratory |
| Synonyms: | Alpha Thalassemia; Thalassemia; Alpha Globin gene deletion; HBA1; HBA2; Alpha globin gene analysis |
| Clinical Indication: | Genetic test for confirmation of suspected alpha-thalassemia |
| CPT 4 Code: | 81257 |
| Note: |
Background Information for Alpha-Thalassemia (HBA1 and HBA2) 7 Deletions: 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; 95 percent are deletions.
Mutations Tested: -α3.7,-α4.2,-(α)20.5,--SEA,--MED,--FIL,--THAI
Clinical Sensitivity: Varies by ethnicity, may be as high as 90 percent.
Methodology: Polymerase chain reaction (GAP-PCR) and gel electrophoresis
Analytical Sensitivity and Specificity: 99 percent.
Limitations: Rare alpha globin gene deletions, non-deletion mutations including gene duplications, and mutations of the regulatory region will not be detected. Diagnostic errors can occur due to rare sequence variations. References: OMIM numbers: alpha-thalassemia (604131), HBA1 (141800), HBA2 (141850). https://www.ncbi.nlm.nih.gov/books/NBK1435/ https://ghr.nlm.nih.gov/condition/alpha-thalassemia
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