What is the recommended work‑up to differentiate beta‑thalassemia trait from hereditary hemochromatosis in a patient with microcytic anemia?

Differentiating Beta-Thalassemia Trait from Hereditary Hemochromatosis in Microcytic Anemia

Begin with serum ferritin and transferrin saturation testing, followed by hemoglobin electrophoresis to distinguish beta-thalassemia trait (which presents with microcytic anemia, normal or low ferritin, and elevated HbA2) from hereditary hemochromatosis (which typically presents with elevated ferritin and transferrin saturation ≥45%). 1

Initial Laboratory Testing

Iron Studies

• Measure serum ferritin and transferrin saturation simultaneously as the essential first step for evaluating suspected hemochromatosis 1, 2
• Use diagnostic thresholds of ferritin >300 µg/L in men or >200 µg/L in women, and transferrin saturation ≥45% to identify potential hemochromatosis 1, 2
• Beta-thalassemia trait characteristically shows normal or elevated ferritin with normal transferrin saturation, distinguishing it from classic hemochromatosis which presents with elevated transferrin saturation as the earliest marker 2, 3

Complete Blood Count Analysis

• Beta-thalassemia trait demonstrates marked microcytosis (MCV 60-70 fL) and hypochromia (MCH 19-23 pg) with normal or mildly elevated red blood cell count 4, 5
• Hemochromatosis typically does not cause microcytic anemia unless advanced iron overload has developed 3
• The presence of microcytosis with elevated red cell count strongly suggests thalassemia trait rather than iron deficiency or hemochromatosis 4

Hemoglobin Analysis

Hemoglobin Electrophoresis or HPLC

• Perform hemoglobin electrophoresis or high-performance liquid chromatography (HPLC) to measure HbA2 levels 4, 5
• Beta-thalassemia trait shows elevated HbA2 (>3.5%) in approximately 90% of cases, which is the most decisive test for beta-carrier detection 4, 5
• Normal HbA2 levels effectively exclude beta-thalassemia trait in most cases 4

Genetic Testing Algorithm

When to Proceed with HFE Testing

• Order HFE gene mutation analysis (C282Y and H63D) only if transferrin saturation ≥45% and/or ferritin is elevated above normal ranges 1, 2
• The American College of Physicians recommends genetic testing after confirming elevated iron studies or when there is a positive family history of hereditary hemochromatosis 1

Pre-Test Counseling Requirements

• Before ordering HFE genetic testing, discuss with the patient: available treatment (phlebotomy) and its efficacy, costs of testing and monitoring, implications for insurability and employment, psychological impact of disease labeling, and family screening implications 1, 2

Critical Diagnostic Patterns

Beta-Thalassemia Trait Pattern

• Microcytic anemia (MCV 60-70 fL, MCH 19-23 pg) 4
• Normal or elevated red blood cell count 4
• Normal or low ferritin levels 3, 4
• Normal transferrin saturation 3
• Elevated HbA2 >3.5% 4, 5

Hereditary Hemochromatosis Pattern

• Transferrin saturation ≥45% (earliest and most sensitive marker) 2, 6
• Elevated ferritin (>300 µg/L in men, >200 µg/L in women) 1, 2
• Normal MCV and MCH (unless advanced disease) 3
• Normal HbA2 4
• Confirmed by HFE genetic testing showing C282Y homozygosity in >90% of cases 2, 7

Important Caveats and Pitfalls

Coexistence of Both Conditions

• Beta-thalassemia trait can coexist with hereditary hemochromatosis and may aggravate iron accumulation in C282Y homozygotes, leading to higher rates of iron overload and severe complications 8, 9
• If a patient with confirmed beta-thalassemia trait has elevated ferritin and transferrin saturation, proceed with HFE genetic testing to exclude coexistent hemochromatosis 8, 9
• The H63D mutation in combination with beta-thalassemia trait may increase iron loading risk 9

False Elevations of Ferritin

• Ferritin can be falsely elevated due to inflammation, chronic liver disease, malignancy, and other inflammatory conditions, making it less specific than transferrin saturation 2, 6
• Always interpret ferritin in context with transferrin saturation and clinical presentation 2

Iron Deficiency Considerations

• Exclude iron deficiency before diagnosing beta-thalassemia trait, as both cause microcytic anemia 4, 5
• Iron deficiency shows low ferritin (<30 µg/L), low transferrin saturation, and normal HbA2 4
• Beta-thalassemia trait shows normal or elevated ferritin, normal transferrin saturation, and elevated HbA2 4, 5

Diagnostic Algorithm Summary

1. Order CBC with red cell indices, serum ferritin, and transferrin saturation simultaneously 1, 2
2. If microcytic anemia with normal/low ferritin and normal transferrin saturation → proceed with hemoglobin electrophoresis to measure HbA2 4, 5
3. If elevated HbA2 >3.5% → diagnose beta-thalassemia trait 4
4. If transferrin saturation ≥45% and/or elevated ferritin → proceed with HFE genetic testing for C282Y and H63D mutations 1, 2
5. If both beta-thalassemia trait and elevated iron studies are present → test for HFE mutations to identify coexistent hemochromatosis 8, 9