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We would like to thank Dr Li for his interest in our article.

At the time of the study, DNA diagnosis of homozygous α0-thalassemia on chorionic villi or amniotic fluid cells was not established at the Guangzhou Maternal and Neonatal Hospital (MNH). Cordocentesis and hemoglobin analysis was the standard diagnostic method for Hb Bart's disease, or homozygous α0-thalassemia, at MNH. This is an acceptable prenatal diagnostic method for the condition.

At-risk couples at both centers were identified either because of previously affected pregnancies, or because antenatal screening using measurement of mean corpuscular volume (MCV) followed by hemoglobin study showed that the couples were α-thalassemia carriers. PCR based diagnosis of α0-thalassemia on maternal or paternal blood was available at MNH, and would be performed to confirm α0-thalassaemia for the at-risk couples.

Carriers of common α-globin gene deletions (--SEA, -α3.7, -α4.2) in southern China can be differentiated by MCV screening. In a study by Ma et al.1 on thalassemia screening in Hong Kong based on MCV and mean corpuscular hemoglobin (MCH) analysis for SEA deletion (n = 110), β-thalassemia (n = 66), single α-globin gene deletion and mutation (n = 70) and hemoglobin E (n = 9), an MCV cut-off of 80 fL or MCH cut-off of 27 pg detected all heterozygous carriers of SEA deletion, but not carriers of α+-thalassemia (-α3.7, -α4.2).

References

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K. Y. Leung*, * Department of Obstetrics and Gynecology, The University of Hong Kong, Queen Mary Hospital, Hong Kong