ABSTRACT
Hb Tak is one of more than 200 high affinity haemoglobin variants reported worldwide. It resultsfrom the insertion of two nucleotides (AC) at the termination codon, between codon 146 and codon147 of the beta-globin gene [Beta 147 (+AC)]. Polycythaemia is the main clinical feature althoughaffected carriers are usually asymptomatic and do not require intervention. Several case studies inthis region have reported the co-inheritance of Hb Tak with Hb E, delta beta and beta thalassaemiawith one case of homozygous Hb Tak in a Thai boy. In this case report, a cluster of haemoglobinTak was found in a family of Malay ethnic origin. Cascade family screening was conducted whileinvestigating a 4-year old girl who presented with symptomatic polycythaemia. She had 2 previousHb analysis done, at 7-month and 2-year-old with the diagnosis of possible Hb Q Thailand andHomozygous Hb D, respectively. Both diagnosis did not fit her clinical presentations. She was plethoric,had reduced exercise tolerance as well as cardiomyopathy. Her parents were consanguineouslymarried and later diagnosed as asymptomatic carriers of Hb Tak. Consequently, re-analysis of thegirl’s blood sample revealed a homozygous state of Hb Tak. In conclusion, high oxygen affinityhaemoglobin like Hb Tak should be considered in the investigation of polycythaemic patients withabnormal Hb analyses. In this case, DNA analysis was crucial in determining the correct diagnosis.
ABSTRACT
HbA1c is an established index of glycaemic control and correlates strongly with risk of chronic diabetic complications. However, the accuracy of HbA1c measurement can be affected by many factors, among which is the presence of haemoglobin (Hb) variants. The aim of the study was to determine the percentage of Hb variant detected during HbA1c monitoring in Hospital Kuala Lumpur. The study also analysed non-reportable HbA1c results in the presence of Hb variants. A cross-sectional study using retrospective data of HbA1c results over fi ve months’ period was analysed on Biorad Variant II Turbo, a high performance liquid chromatography (HPLC) assay. The Hb variants were grouped either as HbS, HbC, others (Hb variant apart from HbS or C), and a combination of HbS or C with Others. A total of 11,904 patients were included. Only 2.3% (273) had Hb variants; HbS trait (10.3%), others (89%), and the combination of HbS trait with others (0.7%). No patient with HbC variant or its combination was found. Only 2.2% of those with Hb variant had non-reportable HbA1c. Although the percentage of Hb variants detected during HbA1c analysis and non-reportable HbA1c results were low, their presence should be noted.
ABSTRACT
Haemoglobin (Hb) abnormalities though quite frequent, are generally detected in populations during surveys and programmes run for prevention of Hb disorders. Several methods are now available for detection of Hb abnormalities. In this review, the following are discussed: (i) the methods used for characterization of haemoglobin disorders; (ii) the problems linked to diagnosis of thalassaemic trait; (iii) the strategy for detection of common Hb variants; and (iv) the difficulties in identification of rare variants. The differences between developing and industrialized countries for the strategies employed in the diagnosis of abnormal haemoglobins are considered. We mention the limits and pitfalls for each approach and the necessity to characterize the abnormalities using at least two different methods. The recommended strategy is to use a combination of cation-exchange high performance chromatography (CE-HPLC), capillary electrophoresis (CE) and when possible isoelectric focusing (IEF). Difficult cases may demand further investigations requiring specialized protein and/or molecular biology techniques.