INTRODUCTION: Haemoglobin Bart's (Hb Bart's) level is associated with α-thalassaemia traits in neonates, enabling early diagnosis of α-thalassaemia. The study aimed to detect and quantify the Hb Bart's using Cord Blood (CB) and CE Neonat Fast Hb (NF) progammes on fresh and dried blood spot (DBS) specimen respectively by capillary electrophoresis (CE).
METHODS: Capillarys Hemoglobin (E) Kit (for CB) and Capillarys Neonat Hb Kit (for NF) were used to detect and quantify Hb Bart's by CE in fresh cord blood and dried blood spot (DBS) specimens respectively. High performance liquid chromatography (HPLC) using the β-Thal Short Programme was also performed concurrently with CE analysis. Confirmation was obtained by multiplex ARMS Gap PCR.
RESULTS: This study was performed on 600 neonates. 32/600 (5.3%) samples showed presence of Hb Bart's peak using the NF programme while 33/600 (5.5%) were positive with CB programme and HPLC methods. The range of Hb Bart's using NF programme and CB programme were (0.5-4.1%) and (0.5-7.1%), respectively. Molecular analysis confirmed all positive samples possessed α-thalassaemia genetic mutations, with 23/33 cases being αα/--SEA, four -α3.7/-α3.7, two αα/-α3.7 and three αα/ααCS. Fifty Hb Bart's negative samples were randomly tested for α-genotypes, three were also found to be positive for α-globin gene mutations. Thus, resulting in sensitivity of 91.7% and 88.9% and specificity of 100% for the Capillarys Cord Blood programme and Capillarys Neonat Fast programme respectively.
CONCLUSION: Both CE programmes using fresh or dried cord blood were useful as a screening tool for α-thalassaemia in newborns. All methods show the same specificity (100%) with variable, but acceptable sensitivities in the detection of Hb Bart.
Alpha thalassaemia is highly prevalent in the plural society of Malaysia and is a public health problem. Haematological and molecular data from 5016 unrelated patients referred from various hospitals to the Institute for Medical Research for α thalassaemia screening from 2007 to 2010 were retrieved. The aims of this retrospective analysis were to describe the distribution of various alpha thalassaemia alleles in different ethnic groups, along with their genotypic interactions, and to illustrate the haematological changes associated with each phenotype. Amongst the patients, 51.2% (n = 2567) were diagnosed with α thalassaemia. Of the 13 α thalassaemia determinants screened, eight different deletions and mutations were demonstrated: three double gene deletions, --(SEA), --(THAI), --(FIL); two single-gene deletions, α-³·⁷ and -α⁴·²; and three non-deletion mutations, Cd59G > A (haemoglobin [Hb] Adana), Cd125T > C (Hb Quong Sze) and Cd142 (Hb Constant Spring). A high incidence of α-³·⁷ deletion was observed in Malays, Indians, Sabahans, Sarawakians and Orang Asli people. However, the --SEA deletion was the most common cause of alpha thalassaemia in Chinese, followed by the α-³·⁷ deletion. As many as 27 genotypic interactions showed 1023 α thalassaemia silent carriers, 196 homozygous α⁺ thalassaemia traits, 973 heterozygous α⁰ thalassaemia carriers and 375 patients with Hb H disease. Statistical analysis showed a significant difference in the distribution of α thalassaemia determinants amongst the various ethnic groups. Hence, the heterogeneous distribution of common determinants indicated that the introduction of an ethnicity-targeted hierarchical α thalassaemia screening approach in this multi-ethnic Malaysian population would be effective.