Hemoglobin A2 Reference Ranges in Neonates
The provided evidence does not contain specific reference ranges for Hemoglobin A2 in neonates, as all guideline and research materials focus on total hemoglobin, hematocrit, and complete blood count parameters rather than hemoglobin electrophoresis fractions.
Critical Timing Considerations for Hemoglobin A2 Measurement
Hemoglobin A2 measurement should not be performed for definitive thalassemia diagnosis until 6 months of age, when hemoglobin patterns have stabilized. 1
- Interpreting hemoglobin electrophoresis results in infants under 6 months using adult reference ranges will lead to misdiagnosis. 1
- At birth and during the neonatal period, fetal hemoglobin (HbF) predominates, making Hemoglobin A2 levels unreliable for diagnostic purposes. 1
Recommended Diagnostic Approach
For suspected thalassemia in neonates, defer definitive hemoglobin electrophoresis until 6 months of age and use age-appropriate, analyzer-specific, and reagent-specific reference ranges. 1
- High-performance liquid chromatography (HPLC) or microcolumn chromatography should be used for precise Hb A2 measurement when the infant reaches appropriate age. 1
- Age-specific reference ranges are essential for accurate interpretation in children under 1 year, as applying adult ranges can misclassify up to 30% of normal children as abnormal. 2
Clinical Pitfalls to Avoid
- Never use adult reference ranges for neonatal hemoglobin fractions, as developmental hemostasis creates marked physiological differences in hemoglobin composition. 3
- Do not attempt definitive thalassemia diagnosis based on Hemoglobin A2 levels in the neonatal period, as the predominance of fetal hemoglobin makes interpretation unreliable. 1
- When thalassemia is suspected based on low MCV with normal or elevated ferritin, use RDW to differentiate: RDW ≤14% suggests thalassemia minor, while RDW >14% suggests iron deficiency. 1
Alternative Neonatal Assessment
While awaiting appropriate age for Hemoglobin A2 measurement, focus on total hemoglobin and hematocrit values that are gestational and postnatal age-dependent. 4, 5, 6, 7