α-Thalassemia: Genotypic Profile Associated with Ethnicity and Hematological Differentiation of Iron Deficiency Anemia in the Region of Uberaba, Minas Gerais, Brazil

Abstract

α-Thalassemia (α-thal) is a hereditary hemoglobinopathy characterized by microcytic anemia due to impaired production of α chains of human globin. Brazilian studies show that the most common genotype is an -α(3.7) deletion with the loss of one or two α genes. As the production of α chains is not as accentuated in these cases, the correct diagnosis can only be achieved through molecular analysis that is not usually routinely performed by laboratories. We investigated the occurrence of α-thal babies born between September 2011 to January 2013 at the hospital of the Universidade Federal do Triângulo Mineiro (UFTM), Uberaba, Brazil, and blood donors of the Uberaba Regional Blood Center, Hemominas Foundation, Uberaba, Brazil, correlating it with ethnicity and differences between hematological parameters of donors, α-thal and iron deficiency patients. α-Thalassemia was investigated for the most common deleted alleles (-α(3.7), -α(4.2), - -(SEA), - -(FIL), - -(THAI), -(α)(20.5) and - -(MED)). The incidence in newborns was 13.16% with a predominance of heterozygosity for the -α(3.7) genotype (12.35%), followed by the -α(3.7)/-α(3.7) (0.46%) and αα/-α(4.2) genotypes (0.35%). In blood donors, the prevalence of α-thal was 14.89%, with all cases being heterozygous for the -α(3.7) deletion. There was an association of the α-thal genotype with African ancestors for both groups, thereby confirming published data and showing the strong influence of Blacks on the composition of the population of Brazil's southeastern region. Minor changes were found between hematological parameters of blood donors with iron deficiency and α-thal that did not contribute to the differential diagnosis between the two types of anemia.

Deletional Alpha-Thalassemia Alleles in Amazon Blood Donors

“…e α-thalassemia alleles frequency found from the random blood donors' samples is similar to that estimated in other studies from Brazilian population (average among 2.5-8%). Our study showed lower α-thalassemia frequency when compared to 14.89% reported in the Uberaba Regional Blood Center's (Hemominas Foundation, Uberaba, Brazil) work, with all cases being heterozygous for the -α 3.7 deletion [21][22][23].…”

Fisiopatogenia e métodos diagnósticos das anemias hemolíticas: uma revisão integrativa.

“…Quando um gene é afetado, acarreta em um portador silencioso, e se dois genes são mutados, resulta no traço α-talassemico. Já a Doença da Hemoglobina H ocorre quando três genes são impactados e a síndrome da Hidropisia Fetal quando os quatros genes alfa estão comprometidos 13,14,15 .…”

Causes of microcytic anaemia and evaluation of conventional laboratory parameters in the differentiation of erythrocytic microcytosis in blood donors candidates

“…Anemia, and particularly IDA, is one of the factors that leads to deferral of blood donor candidates with multiple blood donations being recognized as a cause of ID and anemia [6,9,13,14].…”

“…Some studies have shown that IDA is the main cause of ineligibility in blood donors, especially among women, as observed in this study (Women: 38.2% vs. Men: 1.9%). This result is explained by blood loss during menstrual cycles or gestations [1,5,9,15,16]. In addition to the main related causes, studies have also shown that the frequency of donations may be a potential risk factor for ID [10,14].…”

“…The diagnosis of α-thal is usually reached by evaluating and quantifying fractions of hemoglobin by electrophoresis and by screening for deletions that affect the α-globin gene [4,7,9]. Knowledge and detection of blood donor candidates with these genetic alterations are extremely important for public health since, because of their high incidence and their chronic character with wide clinical variability, they affect the health system as a whole [7][8][9]. Failure to identify α-thal in blood donors, who are usually physically healthy individuals without great comorbidities, may cause misdiagnoses and subsequently lead to incorrect or unnecessary treatment [9,10].…”