Reference Interval:
Less than 1.0%
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| Interpretive Data: |
α-Thalassemia is caused by underproduction of the α-globin chains that make up hemoglobin molecules. Hb A (α2 β2) and Hb A2 (α2delta2) contain α-chains and therefore are insufficiently produced in α-thalassemia. In this condition, γ-globin genes become active early in life, producing homotetramers of γ (γ4 or Hb Bart). After the first few months of life, when β-chain production is established, homotetramers of β (β4 or Hb H) become predominant. Demonstration of either Hb Bart or Hb H in the blood is proof of reduced α-chain production, and hence α-thalassemia. Accurate genotyping of patients with different amounts of Hb Bart will depend on family studies, hematological parameters, and DNA analysis.
| Patient State
| Newborn Hb Bart Level
| | Normal
| Less than 1%
| | α+ thalassemia
| 1-3%
| | α° thalassemia
| 3-10%
| | Hb H Disease
| 15-30%
| | Hydrops Fetalis
| 80-100%
|
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| CPT Code(s): |
83021
|
Cross References: |
Alpha Thalassemia Analysis, Bart, Hemoglobin
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