Hemoglobin (Hb) A2, Quantitative

TEST: 121060
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CPT: 83020
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Synonyms

  • A2, Quantitative
  • Hb A2, Quantitative

Test Includes

Capillary electrophoresis (CE) is performed initially. If an abnormal hemoglobin is detected, appropriate testing will be performed at an additional charge.

Special Instructions

Specify on the request form the patient's race or ethnic origin (if known) as well as the date of any transfusions administered within the preceding three months.

Expected Turnaround Time

2 - 5 days

Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.

Related Documents

Specimen Requirements

Specimen

Whole blood

Volume

1 mL

Minimum Volume

0.5 mL (Note: This volume does not allow for repeat testing.)

Container

Lavender-top (EDTA) tube

Collection

To avoid delays in turnaround time, please submit a separate lavender-top tube for each test requiring a lavender-top.

Storage Instructions

Refrigerate at 2°C to 8°C.

Stability Requirements

Temperature

Period

Room temperature

14 days

Refrigerated

14 days

Frozen

14 days

Freeze/thaw cycles

Stable x3

Patient Preparation

Fasting or fluid restriction is not necessary.

Causes for Rejection

Clotted specimen

Test Details

Use

Investigate for hemolytic anemia, hemoglobinopathies, and thalassemia

Limitations

Blood transfusion prior to hemoglobin analysis may cause inconsistent interpretation.

Methodology

Capillary electrophoresis (CE)

Reference Interval

See table.

Age

Percentage

<7 m

Not established

7 m to 1 y

1.9% to 2.8%

≥2 y

1.8% to 3.2%

Additional Information

Hemoglobin A2 levels have special application to the diagnosis of β-thalassemia trait, which may be present even though peripheral blood smear is normal. (This reflects the underlying genetic spectrum of β-thalassemia, which in reality is a complex of 20 to 30 distinct conditions.) The microcytosis and other morphologic changes of beta-thalassemia trait must be differentiated from iron deficiency. Low MCV may include the majority of β-thalassemia trait patients but does not differentiate iron deficient individuals. Low Hb A2 levels occur in untreated iron deficiency. If the β-thalassemia is associated with iron deficiency, the Hb A2 level falls, making the differentiation even more difficult (corrected after iron therapy).1 The most definitive evidence for presence of β-thalassemia trait is genetic (family study). Offspring of a person with thalassemia major will have beta-thalassemia trait. Hb A2 may be increased in megaloblastic anemia and may be decreased in sideroblastic anemia, Hb H disease, and erythroleukemia.

Footnotes

1. Wasi P, Disthasongchan P, Na-Nakorn S. The effect of iron deficiency on the levels of hemoglobins A2 and E. J Lab Clin Med. 1968 Jan;71(1):85-91.5635011

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
121060 Hgb A2, Quant 121694 Hgb A2 % 4552-6
121060 Hgb A2, Quant 121676 Reflex to HPLC N/A
Reflex Table for Reflex to HPLC
Order Code Order Name Result Code Result Name UofM Result LOINC
Reflex 1 121699 Hgb A2 by HPLC 121714 Hgb A2 % 42245-1

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