At what minimum age can hemoglobin (Hb) electrophoresis be performed to diagnose thalassemia in infants?

Hemoglobin Electrophoresis Timing for Thalassemia Diagnosis in Infants

Hemoglobin electrophoresis can be performed at birth using cord blood or dried blood spots for thalassemia screening, though interpretation requires age-specific reference ranges and definitive diagnosis is often delayed until 6 months of age when hemoglobin patterns stabilize.

Neonatal Screening (Birth to 6 Months)

Immediate Testing Capability

• Hemoglobin electrophoresis or isoelectric focusing (IEF) can be performed on newborn dried blood spots at birth to detect thalassemia-related hemoglobin patterns 1
• Cord blood samples are suitable for initial hemoglobin analysis, showing Hb A at 21.14±7.04% and Hb F at 78.39±7.59% in normal newborns 2
• Neonatal screening using IEF on dried blood spots can identify α-thalassemia (via Hb Bart's detection) and Hb E disorders with acceptable reliability when using appropriate cut-off values 1

Critical Interpretation Considerations

• The first 6 months of life involve dramatic hemoglobin fraction changes that complicate interpretation 2
• Hb A increases substantially from ~21% at birth to 83.38±1.31% by 6 months of age 2
• Hb A2 rises from 0.32±0.19% at birth to a plateau of 2.78±0.25% at 6 months 2
• Hb F decreases rapidly from 78.39±7.59% in cord blood during the first 6 months 2

Optimal Timing for Definitive Diagnosis

Six Months as the Practical Threshold

• Hemoglobin patterns stabilize by 6 months of age, making this the preferred time for definitive thalassemia diagnosis using hemoglobin electrophoresis 2
• By 6 months, Hb A2 levels reach adult-like plateaus, allowing reliable detection of β-thalassemia trait (elevated Hb A2) 2
• Age-specific reference ranges are essential for accurate interpretation in children under 1 year 2, 3

Detection of Specific Thalassemia Types

For α-thalassemia:

• Hb Bart's presence at birth indicates α-thalassemia, with levels ≥0.25% suggesting α⁺-thalassemia trait (sensitivity 92.86%, specificity 74.0%) 1
• Hb H disease can be identified in newborns through IEF 1

For β-thalassemia:

• β-thalassemia trait detection requires Hb A2 quantification, which is most reliable after 6 months when levels stabilize 2, 4
• Testing should be performed when mean cellular hemoglobin (MCH) is <27 pg 4

For Hb E disorders:

• Hb E can be detected at birth with levels ≥1.5% indicating Hb E trait (100% sensitivity and specificity) 1
• Children aged 6-23 months with Hb E heterozygosity show median Hb E levels of 21.9%, while homozygotes show 85.3% 3

Practical Clinical Algorithm

Immediate Newborn Period (Birth)

• Perform newborn screening via IEF or hemoglobin electrophoresis on dried blood spots or cord blood 1
• Identify high-risk cases (Hb Bart's for α-thalassemia, Hb E presence) 1
• Do not rely solely on neonatal results for definitive diagnosis due to physiologic hemoglobin transitions 2

Follow-up Testing (6 Months and Beyond)

• Repeat hemoglobin electrophoresis at 6 months of age for definitive diagnosis and accurate Hb A2 quantification 2
• Use high-performance liquid chromatography (HPLC) or microcolumn chromatography for precise Hb A2 measurement 4
• Apply age-appropriate reference ranges specific to the analyzer and reagent system used 5

Critical Pitfalls to Avoid

• Never interpret hemoglobin electrophoresis results in infants <6 months using adult reference ranges 5, 2
• Avoid misdiagnosis by recognizing that low MCV with normal or elevated ferritin suggests thalassemia rather than iron deficiency 5, 6
• Use RDW to differentiate: low MCV with RDW >14% suggests iron deficiency, while RDW ≤14% suggests thalassemia minor 5
• Genetic testing provides definitive diagnosis when hemoglobin electrophoresis results are ambiguous or for prenatal diagnosis 1, 4