What is the initial workup and management for a patient suspected of having thalassemia?

Workup for Suspected Thalassemia

Begin with a complete blood count (CBC) showing microcytic anemia (MCV <80 fL), followed by hemoglobin analysis using high-performance liquid chromatography (HPLC) or electrophoresis, and confirm with DNA testing for specific globin gene mutations or deletions. 1, 2, 3

Initial Laboratory Screening

Complete Blood Count Analysis

• Check MCV as the primary screening parameter: values <80 fL suggest possible thalassemia carrier status or disease. 1
• Evaluate the degree of microcytosis and anemia severity to distinguish between carrier states and clinically significant disease. 4, 2
• Look for hemolytic markers including elevated indirect bilirubin and reticulocyte count, which indicate ongoing hemolysis from globin chain imbalances. 5, 4

Hemoglobin Analysis

• Perform hemoglobin electrophoresis or HPLC to detect abnormal hemoglobin patterns and quantify hemoglobin fractions (HbA, HbA2, HbF). 2, 3
• Elevated HbA2 (>3.5%) is characteristic of beta-thalassemia trait, while elevated HbF suggests beta-thalassemia major or intermedia. 6
• In alpha-thalassemia, hemoglobin H (β4 tetramers) may be detected in HbH disease, while hemoglobin Bart's (γ4 tetramers) indicates severe alpha-thalassemia. 1, 4
• Mass spectrometry provides additional precision for detecting hemoglobin structural variants when electrophoresis results are equivocal. 3

Definitive Molecular Diagnosis

DNA Testing Strategy

• DNA testing for deletions or point mutations is the definitive diagnostic test to identify the specific genetic defect. 1
• For alpha-thalassemia, test for common deletions in the alpha-globin gene cluster on chromosome 16, particularly in patients of Southeast Asian, Mediterranean, Middle Eastern, or African ancestry. 1, 4
• For beta-thalassemia, sequence the HBB gene on chromosome 11 to identify one of the >200 known disease-causing mutations (mostly single nucleotide substitutions, small deletions, or insertions). 6
• Massively parallel sequencing (next-generation sequencing) facilitates more precise molecular diagnosis when standard testing is inconclusive. 3

Clinical Severity Assessment

Classification by Transfusion Dependence

• Categorize patients into transfusion-dependent thalassemia (TDT) versus non-transfusion-dependent thalassemia (NTDT) based on whether regular blood transfusions are required for survival. 2
• TDT includes beta-thalassemia major, severe HbE/beta-thalassemia, and some cases of alpha-thalassemia (HbH disease with severe anemia). 2
• NTDT includes thalassemia trait (carriers), thalassemia intermedia, and mild HbH disease. 4, 2

Specific Clinical Phenotypes

• Silent carriers and thalassemia trait patients are asymptomatic with normal life expectancy and require no treatment. 4
• Alpha-thalassemia intermedia (HbH disease) causes hemolytic anemia requiring episodic monitoring but typically not regular transfusions. 4
• Hemoglobin Bart's hydrops fetalis (four alpha-gene deletion) typically results in fetal demise and is the most common cause of non-immune hydrops fetalis in Southeast Asian populations (28-55% of cases). 1
• Beta-thalassemia major presents with hemolytic anemia, growth retardation, and skeletal abnormalities in early childhood, requiring lifelong regular transfusions. 5, 4

Ethnicity-Based Risk Assessment

Population-Specific Considerations

• Consider ethnicity in the diagnostic approach: alpha-thalassemia is most prevalent in Southeast Asian, Mediterranean, Middle Eastern, and African populations, while beta-thalassemia is common in Mediterranean, Middle Eastern, and South Asian populations. 1, 6
• Failure to consider ethnicity can lead to missed diagnoses, particularly in populations where carrier rates are high (up to 10-15% in some Mediterranean regions). 1

Family Testing and Genetic Counseling

Cascade Testing Approach

• Test the affected family member first to identify the specific genetic mutation, followed by targeted testing of at-risk family members. 1
• Both parents should undergo MCV screening and genetic testing when one parent is identified as a carrier. 1
• Pre-test counseling should address diagnosis confirmation, reproductive planning implications, and testing limitations. 1

Prenatal Diagnosis Indications

• When both parents are carriers, offer prenatal diagnosis using amniocentesis or chorionic villus sampling to detect severe forms like Hb Bart's hydrops fetalis or beta-thalassemia major. 1, 4
• Middle cerebral artery Doppler ultrasound assesses for fetal anemia in cases of suspected hydrops fetalis. 1
• Chorionic villus sampling is particularly important for alpha-thalassemia carriers due to increased maternal risk of toxemia and postpartum bleeding with Hb Bart's hydrops fetalis. 4

Common Diagnostic Pitfalls

• Do not rely solely on iron studies to distinguish thalassemia from iron deficiency anemia—both can present with microcytosis, but thalassemia typically shows normal or elevated ferritin with normal/elevated iron stores. 2
• Hemoglobin electrophoresis may appear normal in alpha-thalassemia trait (silent carrier or two-gene deletion), requiring DNA testing for definitive diagnosis. 4, 3
• In beta-thalassemia trait, HbA2 may be falsely normal if concurrent iron deficiency is present; repeat after iron repletion. 6