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Alpha-Globin 4.2-kb Deletion (HBA2) — Whole Blood, Qualitative

Published: August 9, 2026Updated: August 16, 2026

A genetic blood test that checks for a specific 4.2-kilobase deletion involving an alpha-globin gene, most often associated with alpha-thalassemia trait.

Quick summary

["Detecting this deletion may explain mild low-red-blood-cell or microcytic anemia associated with alpha-thalassemia trait."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
55236-4
Short code
HBA2 alpha 4.2kb Del Bld Ql
Synonyms
HBA2 alpha 4.2kb 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 examines blood DNA for a specific 4.2-kilobase deletion affecting an alpha-globin gene. Such deletions are common causes of alpha-thalassemia trait, which may produce smaller red blood cells and mild anemia.

Why might I need this test?

It may be ordered when someone has low hemoglobin or small red blood cells, a family history of alpha-thalassemia, or an abnormal hemoglobin screening result. It can also be part of genetic counseling or carrier testing.

How is the test performed?

A whole-blood sample is collected, and the laboratory analyzes DNA to determine whether the specific 4.2-kilobase deletion is present. The result is reported as detected or not detected.

How do I prepare for the test?

No fasting is usually required. Tell your healthcare professional if you recently received a blood transfusion, because donor blood could affect some genetic test results.

Reference range

Adult: 44-147 U/LN/A

Specimen: whole-blood

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Alpha-Globin 4.2-kb Deletion Test

Frequently asked questions

Does a detected deletion mean I have a serious blood disorder?
Not necessarily. A single 4.2-kilobase alpha-globin deletion commonly causes mild alpha-thalassemia trait rather than severe disease.
Can family members be tested?
Yes. Because alpha-thalassemia is inherited, testing may be recommended for relatives, particularly when a family history or abnormal blood count is present.
Will this test detect every type of alpha-thalassemia?
No. This test looks for one specific deletion and does not detect all alpha-globin variants or other causes of low red blood cells. Broader genetic testing may be needed if suspicion remains.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy