Alpha Thalassemia (HBA1 and HBA2) 7 Deletions (Extended TAT as of 11/20/20-no referral available)
Acceptable first-tier genetic test for confirmation of suspected alpha thalassemia or alpha thalassemia trait. Use to assess for seven common alpha globin gene deletions.
Polymerase Chain Reaction/Gel Electrophoresis
Lavender (EDTA), Pink (K2EDTA), or Yellow (ACD Solution A or B).
Transport 3 mL whole blood. (Min: 1 mL)
Ambient: 1 week; Refrigerated: 1 month; Frozen: 6 months
Background Information for Alpha Thalassemia (HBA1 and HBA2) 7 Deletions:
Characteristics: Alpha (+) thalassemia (silent carrier): Mutation of a single alpha2 globin gene (-α/αα); asymptomatic. Alpha (0) thalassemia (trait): Mutation of both alpha2 globin genes, or deletion of alpha1 and alpha2 globin genes in cis (-α/-α; --/αα); mild microcytic anemia possible. Hemoglobin H disease: Mutation of three alpha globin genes (--/-α); hemolysis with Heinz bodies, moderate anemia, and splenomegaly. Hb Bart Hydrops Fetalis Syndrome: Mutation of four alpha globin genes (--/--); lethal in fetal or early neonatal period.
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 and gel electrophoresis.
Analytical Sensitivity and Specificity: Greater than 99 percent.
Limitations: Rare alpha globin gene deletions, non-deletion mutations, gene duplications, and mutations of the regulatory region will not be detected. Diagnostic errors can occur due to rare sequence variations.
This test was developed and its performance characteristics determined by ARUP Laboratories. It has not been cleared or approved by the US Food and Drug Administration. This test was performed in a CLIA certified laboratory and is intended for clinical purposes.
Counseling and informed consent are recommended for genetic testing. Consent forms are available online.
Laboratory Developed Test (LDT)
|Component Test Code*||Component Chart Name||LOINC|
|0051501||Alpha Thalassemia, 7 Deletions||66502-6|
|2001293||Alpha Thalassemia, Specimen||31208-2|
- alpha globin mutation deletions
- HBA1, HBA2