Alpha-Globin (HBA2) 3.7 kb Deletion, Whole Blood — Qualitative
Detects a 3.7 kilobase deletion in the alpha-globin gene region, a change associated with alpha thalassemia.
["A positive result may identify a genetic form of alpha thalassemia, depending on the findings for the other alpha-globin genes."]
Key facts at a glance
- LOINC
- 55251-3
- Short code
- HBA2 alpha 3.7kb Del Bld Ql
- Synonyms
- HBA2 alpha 3.7kb Del Bld Ql
- Category
- liver
- Sample
- whole-blood
- Container
- Lavender-top (EDTA)
- Units
- N/A
- Ref low
- 44
- Ref high
- 147
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- molgen
- CPT
- 84075
- SNOMED
- 27550007
- Specimen volume
- 3 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
What is this test?
This test looks for a specific 3.7 kilobase deletion affecting the alpha-globin gene region, including the HBA2 gene. This deletion is one known cause of alpha thalassemia and is more common in people with Southeast Asian ancestry, although it can occur in any ancestry group.
Why might I need this test?
It may be ordered when blood counts or hemoglobin studies suggest a hemoglobin disorder, particularly when alpha thalassemia is a concern. It can also be used in family studies or genetic counseling.
How is the test performed?
A whole-blood sample is collected, and the laboratory analyzes DNA to determine whether the 3.7 kilobase deletion is present. The exact laboratory method may vary, and the result is reported as detected or not detected.
How do I prepare for the test?
No special preparation is usually required. Follow any instructions provided by the ordering clinician or laboratory, especially if testing is part of a broader genetic evaluation.
Reference range
Adult: 44-147 U/LN/A
No special preparation required. Avoid fatty meals before the test if possible.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Detecting this deletion may indicate a carrier of alpha thalassemia, including a silent carrier when only one alpha-globin copy is affected. The clinical interpretation depends on the status of the other alpha-globin genes, so this result should be reviewed alongside the complete genetic report. A result that is not detected does not rule out other alpha-thalassemia variants.
Short name
Alpha-thalassemia 3.7 kb deletion test
Frequently asked questions
Does a positive result mean I have alpha thalassemia?
Can I have alpha thalassemia even if this test is negative?
Will this test diagnose every type of thalassemia?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
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Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy