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 alpha-chain and nine beta-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 alpha-globin chain variants including Hbs Q-Thailand, Queens, Siam, Constant Spring and Pakse 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 Pakse were observed but could not be differentiated. In contrast, only one abnormal peak of Hb A was observed for beta-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 beta-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) beta-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.