The Simultaneous Presence of α- and β-Thalassaemia Alleles: A Pitfall of Thalassaemia Screening

Abstract

Objective: To compare the efficacy of routine haematological tests and molecular analysis in the diagnosis of double heterozygous α- and β-thalassaemia. Methods: Screening was carried out in extended family members from 125 families registered in the National Thalassaemia Registry, known to have both α- and β-thalassaemia carriers. Results: Eighty-three individuals from 59 families were identified to be double heterozygous for α- and β-thalassaemia only upon molecular analyses. Among 40 married individuals, 1 was at 25% risk for having β-thalassaemia major children and 6 for having Bart’s hydrops pregnancies. Conclusion: Molecular analysis must be used for the accurate diagnosis of double heterozygous α- and β-thalassaemia for proper risk ascertainment, especially in regions with a high prevalence of both types of thalassaemia.

Screening for β-Thalassaemia Trait in Anaemic Pregnant Women

“…85 fl [13] or MCV ! 80 fl [2] . From a haematological point of view the 1998 guideline advises the quantifi cation of HbA 2 in all patients with MCH !…”

Estimating the burden of α-thalassaemia in Thailand using a comprehensive prevalence database for Southeast Asia

“…One hundred conditional simulations of the model were performed, whereby all of the pixels in the map were jointly simulated such that spatial autocorrelation between the pixels was accounted for. 16 This generated PPDs of allele frequency for each pixel in a 1km x 1km grid of Thailand, which were then used to calculate the mean and 95% Bayesian credible intervals for the predicted allele frequencies.…”

“…While deletions constitute the vast majority of these α-thalassaemia variants, non-deletional variants are typically associated with more severe phenotypes (10-12). Because the geographical distribution of β-thalassaemia largely overlaps with the distribution of α-thalassaemia, it is important to note that their co-inheritance often leads to a reduced imbalance between α-globin and β-globin chains, resulting in a milder thalassaemia phenotype (13-16).…”

α‐Thalassemia: Hb H Disease and Hb Barts Hydrops Fetalis

“…12,25 In Southeast Asia where both αand β-thalassemias are common, some people with the β-thalassemia trait as identified by microcytosis and elevated Hb A 2 level, can also concomitantly harbor α-thalassemia deletions. 26,27 Without correct diagnosis, their risk for begetting offspring with either Hb Barts hydrops fetalis syndrome, Hb H disease, or β-thalassemia major can be missed. 6 In clinical laboratories, Hb H inclusion bodies are traditionally used for the detection of the α 0 -thalassemia trait.…”