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 β-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 β-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 β-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) β- 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.