Test Catalog

Test ID: HGBCE    
Hemoglobin Variant, A2 and F Quantitation, Blood

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

Monitoring patients with sickling disorders who have received hydroxyurea or transfusion therapy


This test is not intended for diagnostic purposes.


This test is not useful for screening purposes.

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

See Benign Hematology Evaluation Comparison in Special Instructions.

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

The treatment of red blood cell sickling disorders may involve many therapeutic modalities. Two of the most important and beneficial are treatment with hydroxyurea and chronic transfusion therapy. Hydroxyurea causes elevation of fetal hemoglobin (Hb F) levels, and transfusion serves to lower the percentage of hemoglobin S (Hb S). Both of these therapeutic modalities act to lessen the number and severity of sickling crises. Thus, periodic monitoring of Hb F and Hb S levels are needed to guide further therapy.

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.


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%



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%



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%










Interpretation Provides information to assist in interpretation of the test results

Clinically, optimal levels of hemoglobin S (Hb S) and fetal hemoglobin (Hb F) are patient specific and depend on a number of factors including response to therapy. This test will be performed by capillary electrophoresis and any detected variant present will be reported as their zone only, including Hb S. No confirmatory functional study, such as sickle solubility, will be performed as this test is designed for quantitative monitoring of previously confirmed hemoglobin fractions.


Information reported: Percentages of hemoglobin A (Hb A), hemoglobin A2 (Hb A2), Hb F and any detected hemoglobin variant present. Variants will be reported as zones and are not specific, even if present in Z5 (Zone S). If the identity of the variant has not been previously confirmed, diagnostic hemoglobin electrophoresis testing is necessary (see HBEL1 / Hemoglobin Electrophoresis Evaluation, Blood).

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

Peaks present in zones Z9, Z7, Z6, Z5, Z4, Z3, and Z2-recently labeled the Z(A), Z(F), Z(D), Z(S), Z(E), Z(A2), and Z(C) zones, respectively-may not represent the hemoglobin fractions the zones are named after as other variants can migrate to these zones, including the S, F, A, and A2 positions.


Although the most common variants are easily detected, many hemoglobin variants are not detected by the capillary electrophoresis method alone or can migrate with, and cannot be discriminated from, common variants. Therefore, this test should not be used for screening purposes due to low sensitivity.


Recent transfusion may mask protein results including hemoglobin electrophoresis, hereditary persistence of fetal hemoglobin (HPFH) by flow cytometry, stability studies, and sickle solubility studies depending on percentage of transfused cells present.


Some hemoglobin variants can originate from the donor blood product and not from the tested recipient. These are typically found in low percentage.


Some hemoglobin variants do not sufficiently resolve from other peaks, which precludes separate quantitation of percentages. These will be reported as a single percentage that represents more than 1 variant.


Some therapies cause artefactual effects in protein studies, including Voxelotor (artefactual peaks). These peaks may vary between samples or patients.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Riou J, Szuberski J, Godart C, et al: Precision of CAPILLARYS 2 for the detection of hemoglobin variants based on their migration positions. Am J Clin Pathol. 2018 Jan 29;149(2):172-180

2. National Heart, Lung, and Body Institute Expert Panel: Evidence-Based Management of Sickle Cell Disease: Expert Panel Report, 2014. NIH Publication No. 02-2117 US Department of Health and Human Services: National Institutes of Health; 2014:1-142

3. Rosse WF, Telen M, Ware R: Transfusion Support for Patients with Sickle Cell Disease. American Association of Blood Banks; 1998

4. Ferster A, Tahriri P, Vermylen C, et al: Five years of experience with hydroxyurea in children and young adults with sickle cell disease. Blood. 2001;97:3268-3632

5. Charache S, Terrin ML, Moore RD, et al: Effect of hydroxyurea on the frequency of painful crises in sickle cell anemia. Investigators of the Multicenter Study of Hydroxyurea in Sickle Cell Anemia. N Engl J Med. 1995 May;332(20):1317-1322

6. Keren DF, Shalhoub R, Gulbranson R, Hedstrom D: Expression of hemoglobin variant migration by capillary electrophoresis relative to hemoglobin A2 improves precision. Am J Clin Pathol. 2012 Apr;137(4):660-664

Special Instructions Library of PDFs including pertinent information and forms related to the test