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PubMed This is a summary of 18 peer-reviewed journal articles Updated
Hematology · Sickle Cell-Beta-Thalassemia

How Doctors Confirm the Diagnosis

At a Glance

Sickle cell-beta-thalassemia is confirmed by follow-up hemoglobin testing after screening, usually with HPLC, IEF, or electrophoresis. Doctors compare HbA, HbS, HbA2, and red-cell size, then use iron studies or HBB DNA testing when results are unclear.

A diagnosis of Sickle Cell-Beta-Thalassemia begins with a suspicion, usually from a newborn screen or a blood test, but it is confirmed through precise laboratory “fingerprinting” of the blood [1][2]. Because this condition involves two different genetic traits working together, the laboratory report can look complex.

From Screening to Confirmation

Most babies in the U.S. are screened for hemoglobin disorders at birth. However, this initial screen is just a “pointer”—it is not the final diagnosis, and its patterns can be influenced by prematurity or recent blood transfusions [3].

  • Newborn Screening: Uses a small amount of blood to look for “patterns.” A baby with this condition might show an FS pattern (mostly fetal and sickle hemoglobin, commonly seen in HbSβ0\beta^{0}) or an FSA pattern (fetal, sickle, and a small amount of adult hemoglobin, commonly seen in HbSβ+\beta^{+}) [3][4]. (Note: An FAS pattern generally indicates a sickle cell trait, not the disease).
  • Confirmatory Testing: Prompt confirmation according to newborn screening programs using more precise methods like HPLC (High-Performance Liquid Chromatography) or IEF (Isoelectric Focusing) is required [5][2]. These tools act like a high-resolution camera, identifying and measuring the percentages of different hemoglobin types in the blood [1].

Understanding the Subtypes: Sβ0\beta^{0} vs Sβ+\beta^{+}

The most important distinction in the diagnosis is whether the “Beta-Zero” or “Beta-Plus” subtype is present. This is generally determined by whether the body can make any “normal” adult hemoglobin (HbA) [6][7].

Note: The following values are illustrative and can vary substantially based on age, the specific beta-plus mutation, assay method, co-existing alpha-thalassemia, or treatments like hydroxyurea or transfusions.

Lab Value HbS β0\beta^{0} (Beta-Zero) HbS β+\beta^{+} (Beta-Plus)
HbA (Adult Hemoglobin) Absent [6][8] Detected (Varies widely, often <14% to 25%) [8][9]
HbS (Sickle Hemoglobin) High (Often >80%) [10] Moderate (Often 60–75%) [9]
HbA2 Elevated (Often $\ge$4%) [10] Elevated (Often $\ge$4%) [10]
MCV (Cell Size) Very Low (Microcytosis) [11] Low (Microcytosis) [9]

HbS β0\beta^{0} is often initially confused with typical sickle cell anemia (HbSS) because neither produces HbA [12]. The “clue” for doctors is the HbA2 level; it is usually higher in beta-thalassemia than in typical sickle cell anemia, though there can be overlap depending on the testing method [10].

The Role of Molecular (DNA) Testing

In many cases, standard blood tests (hemoglobin fractionation) are enough. However, your doctor may order HBB molecular testing (gene sequencing) if [13][14]:

  • There was a recent blood transfusion. While a transfusion will obscure the hemoglobin analysis by adding donor HbA, it does not alter the patient’s underlying DNA sequence, allowing molecular tests to find the true genotype [15].
  • The results are “ambiguous” (it’s hard to tell if it’s HbSS or Sβ0\beta^{0}) [5].
  • You need precise genetic information for family planning.

Molecular testing looks directly at the DNA to identify the specific mutation in the beta-globin gene [1].

Small Cells: Thalassemia or Iron Deficiency?

A hallmark of this condition is microcytosis, meaning the red blood cells are smaller than normal [11], showing up on a lab report as a low MCV.

Because iron deficiency also causes small red blood cells, you cannot assume a low MCV alone confirms thalassemia [16]. Doctors distinguish them by:

  1. Iron Studies: Doctors should check ferritin and transferrin saturation levels [17]. If these are low, iron deficiency is present. Iron supplements should only be taken if a documented deficiency exists.
  2. RBC Count: In thalassemia without iron deficiency, the red blood cell count is often relatively higher, even if the cells are small [18].
  3. The “Smear”: Under a microscope, thalassemia blood often shows “target cells” and “basophilic stippling” (tiny dots inside the cells), which are less common in simple iron deficiency [9][11].

Your Diagnostic Checklist

When you look at the laboratory report, look for these specific pieces of data to understand the full picture [9]:

  • [ ] Hemoglobin Fractions: Percentages for HbS, HbA, HbA2, and HbF.
  • [ ] Method Used: It should state if HPLC, IEF, or Electrophoresis was used.
  • [ ] Complete Blood Count (CBC): Specifically the MCV (size) and MCH (weight of hemoglobin in the cell).
  • [ ] Reticulocyte Count: A measure of how fast the bone marrow is making new red cells [9].
  • [ ] Clinical Interpretation: A written summary by a pathologist or hematologist explaining how these numbers fit the diagnosis.

Common questions in this guide

How is sickle cell-beta-thalassemia confirmed after a newborn screen?
A newborn screen points to a possible hemoglobin disorder but does not make the final diagnosis. Doctors usually confirm it with testing that separates and measures hemoglobin types, such as HPLC, IEF, or electrophoresis, and by reviewing HbS, HbA, HbA2, and HbF.
What do HbA and HbA2 reveal about the sickle cell-beta-thalassemia subtype?
HbA is usually absent in HbSβ⁰ and present in HbSβ⁺, although the amount can vary. HbA2 is often elevated in beta-thalassemia and can help distinguish HbSβ⁰ from HbSS, but results may overlap and must be interpreted with other tests.
Can a blood transfusion affect sickle cell-beta-thalassemia testing?
Yes. Donor red blood cells can add HbA and change the hemoglobin pattern, making hemoglobin testing harder to interpret. A transfusion does not change the patient’s DNA, so HBB molecular testing may help clarify the genotype; clinicians may also decide when to repeat blood tests.
Does a low MCV prove beta-thalassemia?
No. A low MCV means red blood cells are small and can occur with beta-thalassemia or iron deficiency. Ferritin and transferrin saturation, the red blood cell count, and a blood smear help doctors separate these possibilities.
When is HBB genetic testing useful?
HBB molecular testing may be useful when blood-test results are ambiguous, after a recent transfusion, or when a family needs precise information for planning. It examines the beta-globin gene directly and can identify the specific mutation.
What should I look for on a sickle cell-beta-thalassemia lab report?
Look for hemoglobin fractions, the testing method, CBC values such as MCV and MCH, and the reticulocyte count. A written interpretation from a pathologist or hematologist helps explain how the results fit together.

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Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Do the results of the confirmatory blood test (HPLC or IEF) match the initial newborn screening results, or is there a discrepancy?
  2. 2.Does the report show any adult hemoglobin (HbA), and does this confirm the Sβ0 or Sβ+ subtype?
  3. 3.Is the HbA2 level elevated, and how does that help confirm it is beta-thalassemia rather than typical sickle cell anemia?
  4. 4.Given the microcytosis (small red cells), have we ruled out iron deficiency with a ferritin test?
  5. 5.Should we perform molecular HBB gene sequencing to find the exact mutation, and would testing both biological parents help clarify the diagnosis?
  6. 6.If a blood transfusion was given recently, how does that affect these hemoglobin analysis results, and when should we repeat the tests?

References

References (18)
  1. 1

    MALDI-MS in first-line screening of newborns for sickle cell disease: results from a prospective study in comparison to HPLC.

    El Osta M, Benoist JF, Naubourg P, et al.

    Clinical chemistry and laboratory medicine 2024; (62(6)):1149-1157 doi:10.1515/cclm-2023-1250.

    PMID: 38353144
  2. 2

    Use of an automated pyrosequencing technique for confirmation of sickle cell disease.

    de Martino CC, Alencar CS, Loureiro P, et al.

    PloS one 2019; (14(12)):e0216020 doi:10.1371/journal.pone.0216020.

    PMID: 31830127
  3. 3

    High birth prevalence of sickle cell disease in Northwestern Tanzania.

    Ambrose EE, Makani J, Chami N, et al.

    Pediatric blood & cancer 2018; (65(1)) doi:10.1002/pbc.26735.

    PMID: 28766840
  4. 4

    New approach to accurate interpretation of sickle cell disease newborn screening by applying multiple of median cutoffs and ratios.

    Allaf B, Patin F, Elion J, Couque N

    Pediatric blood & cancer 2018; (65(9)):e27230 doi:10.1002/pbc.27230.

    PMID: 29781571
  5. 5

    Newborn screening for sickle cell disease in Jamaica: logistics and experience with umbilical cord samples.

    Serjeant GR, Serjeant BE, Mason KP, et al.

    Journal of community genetics 2017; (8(1)):17-22 doi:10.1007/s12687-016-0283-3.

    PMID: 27796853
  6. 6

    Compound Heterogeneous Sickle Cell-B+ Thalassemia Incidentally Discovered Through Cytological Examination of a Fine-Needle Aspiration Specimen from an Aneurysmal Bone Cyst in a Young Child: A Case Report.

    Meliti A, Muftah S, Saleh D, Habibullah N

    Cureus 2023; (15(1)):e33594 doi:10.7759/cureus.33594.

    PMID: 36779144
  7. 7

    Genotype/Phenotype Correlation of β-Thalassemia in Syrian Patients: A Cross-Sectional Study.

    Shoujaa A, Moasses F, Mukhalalaty Y, et al.

    Hemoglobin 2020; (44(1)):42-46 doi:10.1080/03630269.2019.1709207.

    PMID: 31903828
  8. 8

    The German sickle cell disease registry reveals a surprising risk of acute splenic sequestration and an increased transfusion requirement in patients with compound heterozygous sickle cell disease HbS/β-thalassaemia and no or low HbA expression.

    Allard P, Tagliaferri L, Weru V, et al.

    European journal of haematology 2024; (113(4)):501-509 doi:10.1111/ejh.14259.

    PMID: 38946051
  9. 9

    High-performance liquid chromatography screening reveals HbS/β+-thalassemia double heterozygosity as a pediatric muscular dystrophy mimic.

    López-Medina C, Portell-Rigo IM, González-Iribarren V, et al.

    Laboratory medicine 2026; (57(3)) doi:10.1093/labmed/lmag019.

    PMID: 42018765
  10. 10

    Utility of First-Line Diagnostic Tests and Molecular Methods for Accurate Characterization of Sickle Cell Disorders.

    Yadav DD, Chhabra S, Hira JK, et al.

    International journal of laboratory hematology 2026; (48(3)):652-657 doi:10.1111/ijlh.70079.

    PMID: 41765369
  11. 11

    Compound Heterozygous Sickle Cell-Beta Thalassemia Presenting As Chronic Hemolytic Anemia With Microcytosis and Prominent Left Ventricular Trabeculation: A Case Report.

    Radhakrishnan VK, Kamanuru Govindarajulu A, Rajendran TN, et al.

    Cureus 2026; (18(5)):e108797 doi:10.7759/cureus.108797.

    PMID: 42291950
  12. 12

    Difficulties in the diagnosis of HbS/beta thalassemia: Really a mild disease?

    Uçucu S, Karabıyık T, Azik F

    Journal of medical biochemistry 2022; (41(1)):32-39 doi:10.5937/jomb0-30420.

    PMID: 35291497
  13. 13

    Clinical Utility of Confirmatory Genetic Testing to Differentiate Sickle Cell Trait from Sickle-β+-Thalassemia by Newborn Screening.

    Shook LM, Haygood D, Quinn CT

    International journal of neonatal screening 2020; (6(1)) doi:10.3390/ijns6010007.

    PMID: 32064363
  14. 14

    The Alberta Newborn Screening Approach for Sickle Cell Disease: The Advantages of Molecular Testing.

    Zhou JR, Ridsdale R, MacNeil L, et al.

    International journal of neonatal screening 2021; (7(4)) doi:10.3390/ijns7040078.

    PMID: 34842602
  15. 15

    Value of DNA testing in the diagnosis of sickle-cell anemia in childhood in an environment with a high prevalence of other causes of anemia.

    Mbayabo G, Lumbala Kabuyi P, Ngole M, et al.

    Journal of clinical laboratory analysis 2022; (36(8)):e24593 doi:10.1002/jcla.24593.

    PMID: 35819088
  16. 16

    Differentiation of beta thalassemia trait from iron deficiency anemia by hematological indices.

    Jameel T, Baig M, Ahmed I, et al.

    Pakistan journal of medical sciences 2017; (33(3)):665-669 doi:10.12669/pjms.333.12098.

    PMID: 28811791
  17. 17

    Diagnostic accuracy of mean corpuscular volume in detecting coexisting iron deficiency in patients of sickle cell disorders: A hospital-based study.

    Joshi M, Joshi A

    Journal of family medicine and primary care 2024; (13(7)):2647-2652 doi:10.4103/jfmpc.jfmpc_1552_23.

    PMID: 39071021
  18. 18

    Distinguishing Iron Deficiency Anemia From Beta-Thalassemia Trait: Comparative Analysis of CRUISE Index and Other Traditional Diagnostic Indices.

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    Cureus 2024; (16(7)):e64048 doi:10.7759/cureus.64048.

    PMID: 39114184

This page is for informational purposes only and does not constitute medical advice. A hematologist or other healthcare professional should interpret your or your child’s results, especially after a transfusion.