Co-inheritance of α0 -thalassemia elevates Hb A2 level in homozygous Hb E: Diagnostic implications.

INTRODUCTION: Differentiation of homozygous hemoglobin (Hb) E with and without α0 -thalassemia is subtle on routine hematological ground. We examined in a large cohort of homozygous Hb E if the level of Hb A2 is helpful. METHODS: A total of 592 subjects with homozygous Hb E were recruited from ongoing thalassemia screening program. Additionally, five couples at risk of having fetuses with Hb Bart's hydrops fetalis who were homozygous Hb E were also investigated. Hb analysis was performed using capillary electrophoresis system. Globin genotypes were defined by DNA analysis. RESULTS: Subjects were classified into four groups including pure homozygous Hb E (n=532), homozygous Hb E/α0 -thalassemia (n=48), Hb Constant Spring EE Bart's disease (n=8), and Hb EE Bart's disease (n=4). The levels of Hb A2 were found, respectively, to be 4.97±0.69, 6.64±1.02, 4.86±0.87, and 7.60±1.04%. Among five couples at risk, α0 -thalassemia was identified in three subjects with Hb A2 >6.0%. CONCLUSIONS: Increased Hb A2 level is a useful marker for differentiation of homozygous Hb E with and without α0 -thalassemia. This should lead to a significant reduction in number of referral cases of homozygous Hb E for molecular testing of α0 -thalassemia in routine practice.

Diagnosis of common hemoglobinopathies among South East Asian population using capillary isoelectric focusing system.

INTRODUCTION: We have evaluated an automated capillary isoelectric focusing (cIEF)-based Hb analyzer in diagnosis of hemoglobinopathies commonly found among South East Asian population. METHODS: Study was performed on a cohort of 665 adult Thai subjects and 13 fetal blood specimens obtained at routine thalassemia diagnostic laboratory. Hb analysis was performed using the cIEF system. Thalassemia genotypes were defined by DNA analysis. RESULTS: The system revealed satisfactorily within-run and between-run precision for quantitation of Hb A2 and Hb E (CV: 0.02-0.09%). The reference ranges of Hb A2 and Hb E were 2.6-4.0% and 25.7-33.1%, respectively. The system identified the cases of ß-thalassemia and Hb E disorders correctly. Several thalassemia genotypes and Hb variants were identifiable. However, Hb Constant Spring was separated closely to Hb A2 and Hbs Bart's and H were relatively difficult to be reported due to interfering peaks separating at the same regions. Prenatal diagnosis by fetal blood analysis was found to be accurate for Hb Bart's hydrops fetalis and Hb E-ß0 -thalassemia disease. CONCLUSIONS: The cIEF system could accurately diagnose ß-thalassemia and Hb E carriers and demonstrate many Hb variants found in the region. The system cannot report Hb A2 in the presence of Hb E whereas Hbs Lepore and F are comigrated. Diagnosis of α-thalassemia disease based on Hb H and Hb Bart's might be difficult.

Presumptive diagnosis of common haemoglobinopathies in Southeast Asia using a capillary electrophoresis system.

INTRODUCTION: This study was conducted to examine ability of the Capillarys 2 haemoglobin (Hb) testing system to assist in presumptive diagnosis of common Hb variants found in Southeast Asia including five α-chain and nine ß-chain variants. METHODS: Blood samples with unknown Hb variants sent from other hospitals to our centre for identification were re-analysed using the Capillarys 2 Hb analyser (SEBIA). DNA analyses by allele specific PCR assays were used to establish the final diagnoses. RESULTS: Five α-globin chain variants including Hbs Q-Thailand, Queens, Siam, Constant Spring and Paksé were detected. In heterozygous form, the machine demonstrated clearly two abnormal derivatives of Hbs A and A(2) for the former three variants. Small peaks of Hb Constant Spring and Hb Paksé were observed but could not be differentiated. In contrast, only one abnormal peak of Hb A was observed for ß-globin chain variants including those with more negative charge (Hb J-Bangkok, Hb Hope and Hb Pyrgos) and less negative charge (Hb D-Punjab, Hb S, Hb Korle-Bu and Hb C). Hb Tak, an elongated ß-chain variant was co-separated with Hb F whereas the Hb Malay co-migrated with Hb A in a subject with high Hb A(2) ß- thalassaemia trait. CONCLUSION: The capillary electrophoresis system could clearly demonstrate the presence of abnormal Hbs and provide useful information for presumptive diagnoses in most cases. The Hb analysis results could help in selection of appropriate DNA testing for final diagnoses of these variants.