DNA-based mutation detections versus glucose-6-phosphate dehydrogenase (G6PD) activity as a determinant of the enzyme deficiency

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DNA-based mutation detections versus glucose-6-phosphate dehydrogenase (G6PD) activity as a determinant of the enzyme deficiency

 

Author: Chan, Ling-chim
Title: DNA-based mutation detections versus glucose-6-phosphate dehydrogenase (G6PD) activity as a determinant of the enzyme deficiency
Degree: M.Sc.
Year: 2001
Subject: Glucose-6-phosphate dehydrogenase deficiency
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Dept. of Applied Biology and Chemical Technology
Pages: x, 57 leaves : ill., 1 map ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1551197
URI: http://theses.lib.polyu.edu.hk/handle/200/1754
Abstract: G6PD deficiency is one of the most common human enzymopathies, affecting about 400 million people worldwide. The clinical manifestation of G6PD deficiency vary, from some severe cases of neonatal jaundice, favism and hemolytic anemia to being asymptomatic. It prevails in Hong Kong with about 5 % affected males. The association of this enzyme deficiency with neonatal jaundice and hyperbilirubinaemia in newborns make G6PD deficiency a local health problem and that many of the clinical manifestations can be prevented by avoiding the offending agents. This led to the implementation of a neonatal screening test in Hong Kong since 1984 with the use of a standard enzyme assay. G6PD is an X-linked gene and hence it is expressed as a co-dominant trait in females with a varied range of enzyme activity. The use of enzyme assay on its own may not be able to identify all heterozygotes from the normals. An enzyme activity of 9 IU/g Hb measured spectrophotometrically has been adopted in the neonatal screening laboratory in Kwong Wah Hospital to differentiate heterozygotes from normals, i.e. establish a cut off value. In this project, DNA-based mutation detection methods, such as denaturing gradient gel electrophoresis and single strand conformation polymorphism, were used on the samples around this established cut off value to evaluate the validity of the cut off points used. 195 female samples with G6PD activity of 9 - 12.4 IU/g Hb (designated as normal) were analyzed with denaturing gradient gel electrophoresis and single strand conformation polymorphism to confirm the genotype with respect to G6PD. There were 28 heterozygotes found in the 195 "normal" samples, i.e. false negative. As the cut off point used increased from 9 to 12.4 IU/g Hb, the number of false negative decreased. From the results, it would be more accurate as well as practical that 9.4 IU/g Hb is used instead as the new cut off point. The G6PD variants found were G6PD Canton, G6PD Kaiping, G6PD Gaozhou, G6PD Viangchan, G6PD Mahidol, G6PD Chinese-4, and G6PD Coimbra. They are common among Chinese populations. The result of this investigation shows the significance of mutation detection as a secondary test in verifying the samples around the cut off values for enzyme activity are indeed normal genotypically. A system with an initial enzyme assay followed by a mutation detection of the common mutations for the particular population would be advocated to reduce the level of false results those would otherwise be mis-diagnosed.

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