Hemoglobin Electrophoresis in Diagnosing Thalassemia Trait
Role and Indication
Hemoglobin electrophoresis is essential when a patient presents with severe microcytosis and mild anemia with normal or elevated ferritin levels, as it distinguishes thalassemia trait from iron deficiency anemia and prevents unnecessary gastrointestinal investigation. 1
When to Order Hemoglobin Electrophoresis
Order hemoglobin electrophoresis when microcytosis is present with normal iron studies, particularly in patients with appropriate ethnic background (Mediterranean, Middle Eastern, African, or Southeast Asian descent). 1
Order when MCV is disproportionately low relative to the degree of anemia, as this pattern is characteristic of thalassemia trait rather than iron deficiency. 1, 2
Order when the red blood cell count is elevated despite microcytosis, as this combination strongly suggests thalassemia trait over iron deficiency. 3
The Mentzer index (MCV/RBC count) can guide decision-making: a value <13 suggests thalassemia trait with 98.7% sensitivity and 82.3% specificity, while >13 suggests iron deficiency anemia. 4
Diagnostic Interpretation
Beta-thalassemia trait typically shows elevated hemoglobin A2 levels (>3.5%) on electrophoresis, which is the hallmark finding that confirms the diagnosis. 5, 6
Alpha-thalassemia trait may show normal hemoglobin electrophoresis results, as hemoglobin A2 levels are typically normal or slightly decreased; genetic testing is required for definitive diagnosis in these cases. 6, 7
Hemoglobin electrophoresis can be performed using high-performance liquid chromatography (HPLC) or capillary zone electrophoresis (CE), both providing qualitative and quantitative analysis of hemoglobin components. 7
Critical Clinical Context
Severe microcytosis (MCV <70 fL) with mild anemia and normal ferritin should immediately trigger consideration of thalassemia trait, as iron deficiency typically produces proportionate changes in both MCV and hemoglobin. 2
The combination of microcytosis with normal or low-normal RDW (≤14.0%) suggests thalassemia trait, whereas elevated RDW (>14.0%) suggests iron deficiency anemia. 2
Ordering hemoglobin electrophoresis prevents unnecessary and costly gastrointestinal investigations in patients whose microcytosis is due to thalassemia rather than occult bleeding. 1
Common Pitfalls to Avoid
Do not assume ethnic background alone confirms thalassemia—laboratory confirmation with hemoglobin electrophoresis is mandatory, as presumptive diagnosis based on ethnicity is inadequate. 3
Do not order hemoglobin electrophoresis during active iron deficiency, as low iron stores can suppress hemoglobin A2 levels and produce false-negative results; correct iron deficiency first, then perform electrophoresis. 1, 5
Be aware that combined iron deficiency and thalassemia trait can coexist, masking the typical findings of each condition—if microcytosis persists after iron repletion, repeat hemoglobin electrophoresis. 8
Interpretation under capillary electrophoresis requires caution because hemoglobin A2 is clearly separated from hemoglobin E, and alpha-thalassemia gene interactions can affect the amount of hemoglobin A2/E. 7
When Genetic Testing is Needed
If hemoglobin electrophoresis is normal but clinical suspicion for alpha-thalassemia remains high (severe microcytosis, family history, appropriate ethnicity), proceed to DNA analysis for alpha-globin gene deletions. 6, 7
Next-generation sequencing provides the most accurate diagnosis and can detect mutations that conventional techniques miss, though cost remains a limitation for routine screening. 7
Genetic counseling should be offered to patients with confirmed thalassemia trait, particularly those of reproductive age, to assess risk of severe thalassemia in offspring. 6