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Test ID: HBELC    
Hemoglobin Electrophoresis Cascade, Blood

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Useful For Suggests clinical disorders or settings where the test may be helpful

Diagnosis of thalassemias and hemoglobin variants

 

Evaluation of unexplained microcytosis

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

A large number (>800) of variants of hemoglobin (Hb) have been recognized. They are identified by capital letters (eg, Hb A or Hb S), or by the city in which the variant was first discovered (eg, Hb Koln).

 

Mayo Medical Laboratories receives specimens for this test from a wide geographic area and nearly one-half of all specimens received exhibit abnormalities. The most common abnormality is an increase in Hb A2 to about 4% to 8%, which is diagnostic of beta-thalassemia minor. A wide variety of other hemoglobinopathies also have been encountered. Ranked in order of relative frequency, these are: Hb S (sickle cell disease and trait), C, E, Lepore, G-Philadelphia, H, D-Los Angeles, Koln, Constant Spring, O-Arab, and others. Hb C and S are found mostly in people from west or central Africa and Hb E and H in people from Southeast Asia. Hemoglobin electrophoresis is often used in the evaluation of unexplained microcytosis, thus accounting for the frequent detection of Hb Lepore, which is relatively common in Italians and others of Mediterranean ancestry and in Hb E, which is relatively common in Southeast Asians resettled in the United States; microcytosis is characteristic of both Hb Lepore and Hb E.

 

Alpha-thalassemia is very common in the United States, occurring in approximately 30% of African Americans and accounting for the frequent occurrence of microcytosis in persons of this ethnic group. Some alpha-thalassemias (ie, hemoglobin variants H, Barts, and Constant Spring) are usually easily identified in the hemoglobin electrophoresis protocol. However, alpha-thalassemias that are from only 1 or 2 alpha-globin gene deletions are not recognized. Unfortunately, there is no easy test for the diagnosis of these alpha-thalassemias (see AGPB / Alpha-Globin Gene Analysis).

 

Alpha-thalassemia trait itself is a harmless condition.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

HEMOGLOBIN A

1-30 days: 5.9-77.2%

1-2 months: 7.9-92.4%

3-5 months: 54.7-97.1%

6-8 months: 80.0-98.0%

9-12 months: 86.2-98.0%

13-17 months: 88.8-98.0%

18-23 months: 90.4-98.0%

> or =24 months: 95.8-98.0%

 

HEMOGLOBIN A2

1-30 days: 0.0-2.1%

1-2 months: 0.0-2.6%

3-5 months: 1.3-3.1%

> or =6 months: 2.0-3.3%

 

HEMOGLOBIN F

1-30 days: 22.8-92.0%

1-2 months: 7.6-89.8%

3-5 months: 1.6-42.2%

6-8 months: 0.0-16.7%

9-12 months: 0.0-10.5%

13-17 months: 0.0-7.9%

18-23 months: 0.0-6.3%

> or =24 months: 0.0-0.9%

 

VARIANT

No abnormal variants

 

VARIANT 2

No abnormal variants

 

VARIANT 3

No abnormal variants

Interpretation Provides information to assist in interpretation of the test results

The types of hemoglobin present are identified, quantitated, and an interpretive report is issued.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Alpha-thalassemias with only 1 or 2 alpha-globin gene deletions are not recognized by this testing protocol. AGPB / Alpha-Globin Gene Analysis is required to identify 1 or 2 globin gene deletions.

Clinical Reference Provides recommendations for further in-depth reading of a clinical nature

Hoyer JD, Hoffman DR: The Thalassemia and hemoglobinopathy syndromes. In Clinical Laboratory Medicine. Second edition. Edited by KD McMlatchey. Philadelphia, Lippincott Williams and Wilkins, 2002, pp 866-895

Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test