Prevalence of α-Globin Gene Deletions Among Patients with Unexplained Microcytosis in a North-American Population

Abstract

Increasing multi-ethnicity is likely to make alpha-thalassemia (alpha-thal) more prevalent in Western metropolitan areas. Multiplex polymerase chain reaction (m-PCR) allows rapid and precise identification of most of alpha-thal carriers. With this method, we sought to determine the prevalence of alpha-thal and the corresponding genotype, among all non repetitive consecutive blood samples that had an unexplained microcytosis. These specimens had been sent to the hematology laboratory for a blood count analysis, found to be microcytic, and secondarily tested for ferritin level and hemoglobin (Hb) high performance liquid chromatography (HPLC) profile. Five hundred and sixteen microcytic blood samples were evaluated and 197 samples with normal ferritin and Hb HPLC were studied by m-PCR. Among 196 interpretable PCRs, 48 alpha-thal cases (24.5%) were identified: 28 with a single alpha-globin gene deletion and 20 with two alpha-globin gene deletions. Of these 20 cases, six showed two deletions in cis. None of the erythrocytic parameters studied predicted the presence of alpha-thal deletions. We conclude that a significant proportion (24.5%) of blood counts with microcytosis not explained by an iron deficiency, an inflammatory state or an abnormal Hb on HPLC, are caused by an alpha-globin gene deletion. The pertinence of genetic counseling for alpha-thal based on molecular diagnosis should be evaluated more formally in urban centers where this genetic condition is likely to have an increasing prevalence and clinical relevance.

Microcytic hypochromic anemia patients with thalassemia : Genotyping approach

“…Our Þ ndings are in concordance with previous reports, where microcytosis was explained on the basis of α-gene number. [3,[19][20][21][22] The identiÞ cation of α-and β-thalassemia carrier status is important to prevent erroneous and expensive investigations to define the etiology of anemia, as well as prevent unnecessary prolonged iron supplementation. The knowledge of α-and β-gene numbers in α-and β-thalassemia traits in any population is necessary, as it modifies the phenotype of thalassemia by altering the ratio of α-and β-chains of hemoglobin.…”

“…There is limited data reported in the literature for prevalence of α-gene deletion in patients with microcytosis. [3,4] Carriers of α-gene deletion have mild microcytosis with or without anemia. Although anemia is absent or unremarkable, it is important to diagnose α-thalassemia in order to diagnose the cause of microcytosis and to avoid repeated expensive analysis and/ or prolonged iron therapy.…”

Alpha-thalassaemia trait as a cause of unexplained microcytosis in a South African population

“…In their study, other causes of microcytosis such as iron deficiency and β-thalassaemia trait were not excluded from the cohort. A Canadian group [11] yielded a PCR-positive rate of only 24.5% in their unexplained microcytosis cohort. In their study, only 29% of the population were of Asian descent (immigrants), with the remainder being of Canadian descent.…”

Co-inheritance of ?- and ?-thalassemia in a Bangladeshi family

“…In India, -thalassemia is also common and the occurrence of gene frequency is reasonably higher than -thalassemia trait. 5 Though the exact frequency of -andthalassemia is not well characterized in Bangladesh but from the prevalence of carrier rate in our neighboring countries, it is assumed that there is appreciably high frequency ofthalassemia than -thalassaemia. That's why, the co-inheritance of -and -thalassemia is rarely found.…”