Prevalence of α-Thalassemia in the Egyptian Population

Impact of age-dependent red blood cell parameters on α-globin gene genotyping in children

When screening for α-thalassemia in children, adult cut-offs for mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) are generally applied to guide genetic evaluation. However, the normal ranges for MCV and MCH are lower in children than in adults, so we hypothesized that using age-matched cut-offs could lead to a more rational diagnostic strategy. The aim of this study was to evaluate if age-matched cut-offs could be applied advantageously. Data on children referred to a hemoglobin fractionation at the Department of Clinical Biochemistry, Aarhus University Hospital between 2016-2021 were identified in the laboratory information system. α-globin gene (HBA1/HBA2) genotyping was performed using multiplex gap-polymerase chain reaction. A total of 387 children were identified. HBA1/HBA2-genotyping was performed in 207 children (53%), and α-thalassemia was diagnosed in 47 children (23%) with -α3.7/αα being the predominant genotype (13%). We found that 23 children had MCV and MCH levels in the normal age-matched range, and two of these children (9%) were α+ thalassemia carriers with three functional α-globin genes. Using age-specific cut-off levels resulted in a reduction of 23 (11%) genotypes performed. In conclusion, applying age-matched cut-offs for MCV and MCH when screening children for α-thalassemia lead to 11% fewer genotypes performed while 9% carriers of α+ thalassemia (of the medically innocuous genotype -α3.7/αα) would have been overlooked.

The prevalence and outcomes of α- and β-thalassemia among pregnant women in Hubei Province, Central China: An observational study

ABSTRACT

There is no information concerning the prevalence of thalassemia among pregnant women in Hubei Province currently. This study is aimed to explore the prevalence of α- and β-thalassemia genotypes among pregnant women in Hubei Province, and to explore the clinically applicable screening approach, as well as to investigate the pregnancy outcomes of α- and β-thalassemia carriers.Pregnant participants were recruited from 4 hospitals for the screening of α- and β-thalassemia mutations in Hubei Province. Polymerase Chain Reaction and flow cytometry methods were used to examine α- and β-thalassemia mutations. The hematological parameters and pregnancy outcomes of α- and β-thalassemia carriers were obtained from the hospital information system. The chi-square tests were used to evaluate the difference in hematological parameters between pregnant thalassemia carriers and the control group.Among 11,875 participants, 414 (3.49%) were confirmed with α-thalassemia carriers, 228 (1.92%) were confirmed with β-thalassemia carriers, and 3 (0.03%) were confirmed with both α- and β-thalassemia carriers. The frequency of -α3.7 accounted for 2.05% and it was the most frequent genotype of α-thalassemia; the proportion of IVS-II-654 was 0.85% and it was the most frequent genotype of β-thalassemia in Hubei Province. Furthermore, the proportion of patients with low mean corpuscular volume (MCV) or mean cell hemoglobin (MCH) values was accounted for 36.64% and 93.97% among α-thalassemia and β-thalassemia carriers, respectively. And participants with normal MCV and MCH values were accounted for 95.07% among non-thalassemia participants. High prevalence of pregnancy-induced diabetes (16.97%), preterm birth (9.96%), pregnancy-induced hypertension (8.12%), and low birth weight (5.90%) were observed among pregnant thalassemia carriers.MCV and MCH values were suggested to apply on the preliminary screening of pregnant β-thalassemia; however, it's unpractical on that of α-thalassemia. Furthermore, thalassemia carriers might have a high risk of negative pregnancy outcomes. These findings could be useful for the preliminary screening of thalassemia and perinatal care for the pregnant thalassemia carriers.

Umbilical Cord Blood Screening for the Detection of Common Deletional Mutations of α-Thalassemia in Bangladesh

α-Thalassemia (α-thal) is assumed to be very prevalent in Bangladesh. We aimed to assess the prevalence of the disease in the country and provide a model for α-thal newborn screening in Bangladesh. We collected umbilical cord blood (UCB) samples from 413 unrelated newborns in Bangladesh. Demographic information, blood indices, osmotic fragility, serum iron (Fe), and zinc (Zn) levels were evaluated for all the subjects. All subjects underwent a polymerase chain reaction (PCR)-based diagnosis for α-thal status, followed by a multiplex gap-PCR-based identification of the deletion type present. Sixty-seven subjects had at least one α-thal deletion (16.22%). We observed that -α^3.7 (rightward), - -^SEA (Southeast Asian), -α^4.2 (leftward), - -^MED (Mediterranean) and - -^THAI (Thailand) deletions were the most common α-globin deletions present in the country, with the -α^3.7 (n = 37) and - -^SEA (n = 18) being most prevalent. The osmotic fragility test (OFT) could predict the presence of α-thal deletions with over 98.0% sensitivity. Complete UCB count analysis revealed significant differences between healthy subjects and subjects with α-thal deletions. Although the iron level was almost the same (108.0 vs. 105.7 µg/dL), a reduced level of Zn (98.6 vs. 71.8 µg/dL, p < 0.01) was observed in the cord blood-derived serum of the subjects with α-thal deletions. Moreover, parental age at the time of delivery, gestational period, and birth weight was lower in the subjects with α-thal deletions. This study provides partial information on the epidemiology of α-thal in Bangladesh and describes a model for α-thal newborn screening in the country.