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Neonatal screening for α-thalassemia by cord hemoglobin Barts: how effective is it?
1Prenatal Diagnostic Center, Guangzhou Maternal & Neonatal Hospital, Guangzhou Women & Children Medical Center affiliated to Guangzhou Medical University, Guangzhou, Guangdong, China.
Insights
Measuring hemoglobin Bart's (Hb Bart's) in cord blood is a common screening method for alpha-thalassemia. However, this study found Hb Bart's levels are inadequate for detecting silent alpha-thalassemia carriers with specific gene deletions.
Area of Science:
- Genetics
- Hematology
- Molecular Biology
Background:
- Hemoglobin Bart's (Hb Bart's) in cord blood is a recognized indicator for alpha-thalassemia.
- Elevated Hb Bart's levels correlate with the number of defective alpha-globin genes.
Purpose of the Study:
- To evaluate the reliability of Hb Bart's levels in cord blood for screening alpha-thalassemia.
- To assess the effectiveness of Hb Bart's screening for identifying silent carriers, particularly those with the -α(3.7) deletion.
Main Methods:
- Utilized an automatic capillary electrophoresis system to quantify Hb Bart's levels in neonatal blood samples.
- Employed molecular DNA analyses to identify various alpha-thalassemia genotypes and confirm diagnoses.
Main Results:
- Out of 1169 newborns, 69 showed elevated Hb Bart's, with alpha-thalassemia confirmed by DNA analysis.
- Among 1100 newborns with undetectable Hb Bart's, 45 silent carriers of alpha-thalassemia were identified via DNA analysis, all possessing the -α(3.7) deletion genotype.
Conclusions:
- Hb Bart's measurement is insufficient for reliably screening newborns with single alpha-gene mutations, specifically the 3.7-kb deletion.
- The current Hb Bart's screening method is inadequate for detecting all forms of alpha-thalassemia, particularly silent carrier states.
Introduction:
It has long been recognized that the hemoglobin (Hb) Bart's in cord blood is an accurate indicator of α-thalassemia and that the level of Hb Bart's was increased accordingly with the increasing numbers of the defective α-genes.
Methods:
This study used an automatic capillary electrophoresis system to determine the Hb Bart's levels in cord blood. Molecular analyses were used to detect various genotypes of α-thalassemia.
Results:
Sixty-nine of the total 1169 newborns were found to have an increased Hb Bart's in cord blood, in whom the diagnosis of α-thalassemia was confirmed by the DNA analysis. The remaining 1100 newborns had no detectable Hb Bart's at birth; among these, 45 carriers of silent α-thalassemia were diagnosed by DNA analysis. All the 45 cases had only the -α(3.7) deletion genotype.
Conclusion:
For newborns of one α-gene mutation, especially for 3.7-kb deletion, the method based on Hb Bart's is inadequate and is therefore not reliable for screening.
