Test Catalog

Test Name

Test ID: HBELC    
Hemoglobin Electrophoresis Cascade, Blood

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

Diagnosis and comprehensive classification of thalassemias and hemoglobin variants

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

Hemoglobin electrophoresis cascade will always include hemoglobin A(2) and F and hemoglobin electrophoresis utilizing cation exchange HPLC and capillary electrophoresis methods.

 

Hemoglobin electrophoresis reflex testing, performed at additional charge, may include any or all of the following to identify rare hemoglobin variants present: sickle solubility (hemoglobin S screen), hemoglobin heat and isopropanol stability studies (unstable hemoglobin), isoelectric focusing, intact globin chain mass spectrometry (hemoglobin variant by mass spectrometry), Hb F distribution by flow cytometry (hemoglobin F red cell distribution), DNA (Sanger) testing for beta chain variants and the most common beta thalassemias (beta-globin gene sequencing), multiplex ligation-dependent probe amplification (MLPA) testing for beta cluster locus large deletions and duplications, including large deletional hereditary persistence of fetal hemoglobin (HPFH), delta-beta (DBT), delta thalassemias, gamma-delta-beta (GDBT), and epsilon-gamma-delta-beta (EGDBT) thalassemias (beta globin cluster locus del/dup), large deletional alpha thalassemias and alpha gene duplications (alpha-globin gene analysis), alpha chain variants and non-deletional alpha thalassemias (alpha-globin gene sequencing), and gamma chain variants and non-deletional HPFH (gamma globin full gene sequencing).

 

If a Thalassemia/Hemoglobinopathy Patient Information sheet (T358) is received with the sample, the reported clinical features or clinical impression will be considered in the interpretation and focus of the evaluation. Our laboratory has extensive experience in hemoglobin variant identification and many cases can be confidently classified without molecular testing. However, molecular confirmation is always available. If no molecular testing or, conversely, specific molecular tests are desired, utilize the appropriate check boxes on the information sheet. If the information sheet or other communication is not received, the reviewing hematopathologist will select appropriate tests to sufficiently explain the clinical impression or reported CBC results, which may or may not include molecular testing.

 

Hemoglobin (HGB) Electrophoresis Summary Interpretation, an additional consultative interpretation that summarizes all testing, will be provided after test completion to incorporate subsequent results into an overall evaluation if 1 or more of the following molecular tests are reflexed on the HBELC / Hemoglobin Electrophoresis Cascade, Blood:

-ATHAL / Alpha-Globin Gene Analysis

-WASQR / Alpha-Globin Gene Sequencing, Blood

-WBSQR / Beta-Globin Gene Sequencing, Blood

-WBDDR / Beta-Globin Cluster Locus Deletion/Duplication, Blood

-WGSQR / Gamma-Globin Full Gene Sequencing

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

Hemoglobin abnormalities not uncommonly occur as compound disorders (2 or more mutations) that can have complex interactions and variable phenotypes. Although powerful as an adjunct for a complete and accurate diagnosis, genetic methods alone can give incomplete and possibly misleading information due to limitations of the methods. Interpretation of genetic data requires the incorporation of protein analysis results. This profile is well-suited for the classification of hemoglobin disorders.

 

A large number (>1000) 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). Clinical symptoms that can be associated with hemoglobin disorders include microcytosis, sickling disorders, hemolysis, erythrocytosis, cyanosis/hypoxia, long-standing or familial anemia, compensated or episodic anemia, and increased methemoglobin or sulfhemoglobin results.

 

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 indicates beta-thalassemia minor in the correct clinical context. 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 easily identified in the hemoglobin electrophoresis protocol. However, alpha-thalassemias that are from only 1 or 2 alpha-globin gene deletions are not recognized by protein studies alone. For the diagnosis of alpha-thalassemias, deletion and duplication testing is required.

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

No significant cautionary statements.

Clinical Reference Recommendations for 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 Library of PDFs including pertinent information and consent forms, specimen collection and preparation information, test algorithms, and other information pertinent to test.