Hemoglobin patterns in common hemoglobinopathies

Condition	Genotype	Neonatal screening*	By age 6 weeks	Older children (≥5 years), adolescents, and adults
Condition	Genotype	Neonatal screening*	By age 6 weeks	Hb A (%)	Hb A₂ (%)	Hb F (%)	Hb S (%)	Hb C (%)
Normal	AA	FA	FA or AF	95 to 98	2 to 3	<2	0	0
Beta thalassemia trait	A/(β⁰ or β⁺)	FA	FA	90 to 95	>3.5 (unless due to δβ; can be normal or lower)	1 to 3 (significantly higher if due to δβ deletion)	0	0
Sickle cell trait	AS	FAS	FAS	50 to 60	<3.5	<2	35 to 45; may be lower if concomitant alpha thalassemia	0
Homozygous sickle cell (Hb SS) disease	SS	FS	FS	0	<3.5 but may be increased with concomitant α-thalassemia. May be falsely elevated when measured by HPLC	5 to 15; may be higher in rare cases	85 to 95	0
Sickle-β⁰ thalassemia	Sβ⁰	FS	FS	0	>3.5 but may be falsely elevated when measured by HPLC	2 to 15	80 to 92	0
Sickle-β⁺ thalassemia	Sβ⁺	FSA or FS^¶	FSA	3 to 30	>3.5 but may be falsely elevated when measured by HPLC	2 to 10	65 to 90	0
Hb SC disease	SC	FSC	FSC	0	<3.5	1 to 5; may be higher in rare cases	45 to 50	45 to 50
Hb CC disease^Δ	CC	FC	FC	0	<3.5	<2	0	95
Hb C trait^Δ	AC	FAC	FAC	50 to 60	<3.5	<2	0	40 to 50

Hemoglobin may be analyzed by one or more of several separation techniques including HPLC, capillary electrophoresis, isoelectric focusing, or gel electrophoresis. Numbers are approximate and may vary depending on the laboratory method used. Transfusions will affect the percentages measured. Levels of Hb A2 can be affected by thalassemia, iron deficiency, and various other conditions and cannot be used to make a diagnosis of Hb S-beta thalassemia. In selected cases, DNA analysis may be helpful. Refer to UpToDate for discussions of hemoglobin analysis and diagnosis of specific syndromes.

Hb: hemoglobin; Hb A: adult hemoglobin; Hb F: fetal hemoglobin; δβ: delta-beta; HPLC: high-performance liquid chromatography; DNA: deoxyribonucleic acid.

* The neonatal screening patterns list the different hemoglobins in order of abundance. As an example, the FAS pattern has the greatest amount of Hb F, followed by Hb A, followed by Hb S.

¶ In sickle-β⁺ thalassemia, the quantity of Hb A at birth may be insufficient for detection.

Δ In Hb C trait, concomitant alpha thalassemia variants lower the percentage of Hb C, and Hb C levels <40% after iron deficiency is excluded or corrected may indicate a two-gene deletion at the alpha locus. Hb C trait plus a beta thalassemia variant could be misdiagnosed as Hb CC disease.

Adapted from: Sickle cell disease in children and adolescents: Diagnosis, guidelines for comprehensive care, and care paths and protocols for management of acute and chronic complications. Revised at the Annual Meeting of the Sickle Cell Disease Care Consortium, Sedona, AZ, November 10-12, 2001.

With additional data from: Bain BJ. Sickle cell haemoglobin and its interactions with other variant haemoglobins and with thalassaemias. In: Haemoglobinopathy Diagnosis, 2nd ed, Wiley-Blackwell, Oxford, 2005.

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Hemoglobin patterns in common hemoglobinopathies