Ordering Recommendation

Acceptable first-tier genetic test for confirmation of suspected alpha thalassemia or alpha thalassemia trait. Assesses for seven common alpha globin gene deletions.

Mnemonic
ALPHA THAL
Methodology

Polymerase Chain Reaction/Gel Electrophoresis

Performed

Varies

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: 1 week; Refrigerated: 1 month; Frozen: 6 months

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.

Compliance Category

Laboratory Developed Test (LDT)

Note
Hotline History
N/A
CPT Codes

81257

Components
Component Test Code* Component Chart Name LOINC
0051501 Alpha Thalassemia, 7 Deletions 66502-6
2001293 Alpha Thalassemia, Specimen 31208-2
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Aliases
  • alpha globin mutation deletions
  • HBA1, HBA2
Alpha Thalassemia (HBA1 and HBA2) 7 Deletions