published_or_final_version / abstract / Pathology / Master / Master of Philosophy

Mutations in the beta-globin (β-globin) gene cause beta-thalassaemia (β-thalassaemia).The screening strategy for β-thalassaemiais based on the value of mean corpuscular volume (MCV) from the complete blood count (CBC) data. Current laboratory practice considers blood samples with MCV higher than 80fL as normal. No further assessment will be done on these samples. However, there are clinically silent β-globin gene mutations with MCV higher than 80fL, for example, heterozygous haemoglobin E (HbE). The importance of finding out this kind of mutations is due to the serious outcome when they occur together with classic β thalassaemia mutations in compound heterozygous states, which may produce a condition mimicking β thalassaemia major. The method used to recognize the presence of clinically silent β-globin gene mutations should be robust and with high sensitivity. High resolution melting (HRM) is a suitable technique to screen gene mutations. It is fast and convenient. The process is completed in a closed system without any post PCR manipulation. The sensitivity is up to a single nucleotide change. Using HRM for mutations screening followed by confirmation with sequencing can reduce time and cost of testing clinically silent β-globin gene mutations on a large scale. This study first shows the ability of HRM in detecting various types of β-globin gene mutations. The technique is then applied to detect clinically silent β-globin gene mutations in a group of high school students with normal CBC data. Mutations with different clinically significance were found. The frequency of mutation found in the samples of the study suggests that screening for β-globin gene mutation may be worthwhile in subjects with MCV higher than 80fL. / published_or_final_version / Pathology / Master / Master of Medical Sciences

The thalassaemias are the commonest monogenic disorders in the world population. They occur at a particularly high frequency in Mediterranean regions and Southeast Asia, which cause a massive public health problem. In Hong Kong, the prevalence of heterozygous carriers of α or β thalassaemia mutations is approximately 8% [1]. Thalassaemia is characterized by the reduced synthesis of one or more normal globin chains. This causes globin chain imbalance and finally leads to hypochromic microcytic anaemia. Different types of thalassaemia are named according to the under-produced chains. The majority of thalassaemia can be diagnosed by basic haematologic profiles and simple phenotypic techniques. However, in some cases of thalassaemia the diagnosis are not apparent after routine laboratory investigations. To arrive at a diagnosis which is important for antenatal diagnosis and genetic counseling, it is necessary to use molecular approaches. In this study, 25 patients with microcytosis, normal phenotypic haemoglobin study results and without iron deficiency were analyzed retrospectively. This cohort of patients was suspected to have occult or masked thalassaemia. DNA was extracted from archive samples and further investigated by alpha multiplex gap polymerase chain reaction (α multiplex gap-PCR), alpha amplification refractory mutation system (α ARMS) and direct nucleotide sequencing of globin genes for the detection of possible underlying globin gene mutations. Results indicated that 60% of these cases with microcytosis were occult and silent αthalassaemia caused by deletional or non-deletional mutations. Maskedβthalassaemia due to co-existing δ thalassaemia or variants or normal Hb A2 β thalassaemia due to mild β globin gene mutations were not detected in the cohort. Forty percent of these cases of microcytosis remained unexplained, which await further molecular testing. / published_or_final_version / Pathology / Master / Master of Medical Sciences

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published_or_final_version / Pathology / Master / Master of Medical Sciences

published_or_final_version / Pathology / Master / Master of Medical Sciences

published_or_final_version / abstract / toc / Medicine / Master / Doctor of Medicine

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences