Alpha Thalassemia (HBA1 and HBA2) 7 Deletions
0051495
Ordering Recommendation
First-tier genetic test for confirmation of suspected alpha thalassemia.
Mnemonic
ALPHA THAL
Methodology
Polymerase Chain Reaction/Gel Electrophoresis
Performed
Mon, Thu
Reported
7-10 days
New York DOH Approval Status
This test is New York DOH approved.
Specimen Required
Patient Preparation
 
Collect
Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).  
Specimen Preparation
Transport 3 mL whole blood. (Min: 1 mL)  
Storage/Transport Temperature
Refrigerated.  
Unacceptable Conditions
 
Remarks
 
Stability
Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable  
Reference Interval
By report
Interpretive Data
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.



Counseling and informed consent are recommended for genetic testing. Consent forms are available online at www.aruplab.com.

See Compliance Statement C: www.aruplab.com/CS
Note
CPT Code(s)
81257
Components
Component Test Code*Component Chart Name
0051501Alpha Thalassemia, 7 Deletions
2001293Alpha Thalassemia, Specimen
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Cross References
  • alpha globin mutation deletions
  • HBA1, HBA2