Quality assessment of e-commerce websites using Bayesian belief networks

This thesis raises the issue of quality in E-commerce websites and addresses methodologies and approaches to standardize their assessment. The thesis blends the knowledge of academic research with the opinions and insights from experts and practitioners in the field to provide a comprehensive view of the issues and their remedies. The most experienced and successful E-commerce companies are beginning to realize that key determinants of success or failure are not merely a web presence or a low price but delivering a high quality website. Recent research shows that price and promotion are no longer the main draws for customers to make a decision on a purchase. More sophisticated online customers would rather pay a higher price to a provider with high quality service. Given that the establishment of an E-commerce website is mainly a software development effort; there are several standards that apply in governing the quality of such development. There seems to be an almost overwhelming abundance of quality standards that lead to a high level of cynicism and skepticism surrounding them and the eventual lack of use. Furthermore, no standard can directly predict the quality a website under development is going to achieve. Past approaches concerning the quality of E-commerce websites emphasize usability standards using techniques like feature inspection and collecting data about end-users' opinion by questionnaires. These methods provide important feedback and their results can be utilized as a useful background for future work, however, they do not contribute directly to a dynamic model that enables forecasting. The study of quality in the domain of the Internet in general, and E-commerce in particular, poses new challenges as technology evolves, including methods and metrics for estimating, managing quality during the product life cycle and quality-of-use measurement. The solution proposed by this research is to use a Bayesian Belief Network model. This model provides a consistent and practical approach to assessing the quality of the website. The assessment can be carried out before the completion of the website development, thus, providing insight on the trend and direction for correction and improvements. It can also be carried out on completed and operational work, providing analysis of areas for improvement. The model should be relatively quick and practical in providing an overall comprehensive assessment with root-cause analysis that would lead to corrective measures to improve the quality of the E-commerce website. In this research idioms were applied in realizing a complete Bayesian Belief Network model. The conclusions are measured against comparative assessment to validate the practical benefits of the work accomplished. The WebQual method was utilized to validate the "belief" established by the model.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Pharmacogenetic allele nomenclature: International workgroup recommendations for test result reporting

This manuscript provides nomenclature recommendations developed by an international workgroup to increase transparency and standardization of pharmacogenetic (PGx) result reporting. Presently, sequence variants identified by PGx tests are described using different nomenclature systems. In addition, PGx analysis may detect different sets of variants for each gene, which can affect interpretation of results. This practice has caused confusion and may thereby impede the adoption of clinical PGx testing. Standardization is critical to move PGx forward

Pharmacogenetic studies of thiopurines : focus on thiopurine methyltransferase

Pharmacogenetics represents the study ofvariability in drug response due to genetic variations. The thiopurines (6-mercaptopurine, 6-thioguanine and azathioprine) are prodrugs which require metabolic transformation to exert effect. Thiopurines are used in inflammatory bowel disease, as maintenance treatment of childhood acute lymphoblastic leukaemia, and for immunosuppression after transplantation. The metabolism is complex and one important enzyme involved is thiopurine methyltransferase (TPMT). Inherited variation in TPMT activity is one factor responsible for individual differences in susceptibility to thiopurine-induced toxicity or in the therapeutic response to thiopurines. The enzyme activity is under controi of agenetic polymorphism. The frequency distribution of TPMT activity in Caucasians is trimodal, with 89% having high enzyme activity, 10% having intermediate activity and l of 300 having almost undetectable activity. The TPMT gene has been characterised and several single nucleotide polymorphisms (SNPs) identified causing decreased enzyme activity. The most common SNPs are TPMT*2, TPMT*3A and TPMT*3C. In the investigations for this thesis we have studied the pharmacogenetics of thiopurines with focus on TPMT. A real-time RT-PCR method was developed for quantification of TPMT gene expression, and a pyrosequencing method was developed for genotyping of TPMT SNPs. TPMT gene expression correlated to enzyme activity in individuals with high enzyme activity. The allele frequencies of TPMT*3A and TPMT*3C in samples from 800 Swedish individuals were in agreement with those in other Caucasian populations, although TPMT*3B was more common and TPMT*2 was rarer. We investigated the concordance between genotype and phenotype and found discordance between genotype and phenotype in two unrelated patients. In these patients, we detected two new sequence variants, TPMT*14 and TPMT*15, which lead to a non-functional TPMT enzyme. The TPMT genotype and phenotype were also determined in the parents of the two patients and the inheritance of these alleles was investigated. Sixty patients with inflammatory bowel disease following a standardised dose escalation schedule of azathioprine or 6-mercaptopurine were closely monitored over the course of 20 weeks. During treatment, the TPMT gene expression decreased. In contrast, TPMT enzyme activity did not change. TPMT heterozygous patients had a lower probability of remaining in the 20week study. Forty-five percent of the patients were withdrawn due to adverse events, but 67% of these tolerated a lower dose of thiopurines. The inosine triphosphate pyrophosphatase polymorphism (ITPA 94C>A) was not associated with occurrences of adverse events

Pharmacogenetic studies of thiopurines : focus on thiopurine methyltransferase

Pharmacogenetics represents the study ofvariability in drug response due to genetic variations. The thiopurines (6-mercaptopurine, 6-thioguanine and azathioprine) are prodrugs which require metabolic transformation to exert effect. Thiopurines are used in inflammatory bowel disease, as maintenance treatment of childhood acute lymphoblastic leukaemia, and for immunosuppression after transplantation. The metabolism is complex and one important enzyme involved is thiopurine methyltransferase (TPMT). Inherited variation in TPMT activity is one factor responsible for individual differences in susceptibility to thiopurine-induced toxicity or in the therapeutic response to thiopurines. The enzyme activity is under controi of agenetic polymorphism. The frequency distribution of TPMT activity in Caucasians is trimodal, with 89% having high enzyme activity, 10% having intermediate activity and l of 300 having almost undetectable activity. The TPMT gene has been characterised and several single nucleotide polymorphisms (SNPs) identified causing decreased enzyme activity. The most common SNPs are TPMT*2, TPMT*3A and TPMT*3C. In the investigations for this thesis we have studied the pharmacogenetics of thiopurines with focus on TPMT. A real-time RT-PCR method was developed for quantification of TPMT gene expression, and a pyrosequencing method was developed for genotyping of TPMT SNPs. TPMT gene expression correlated to enzyme activity in individuals with high enzyme activity. The allele frequencies of TPMT*3A and TPMT*3C in samples from 800 Swedish individuals were in agreement with those in other Caucasian populations, although TPMT*3B was more common and TPMT*2 was rarer. We investigated the concordance between genotype and phenotype and found discordance between genotype and phenotype in two unrelated patients. In these patients, we detected two new sequence variants, TPMT*14 and TPMT*15, which lead to a non-functional TPMT enzyme. The TPMT genotype and phenotype were also determined in the parents of the two patients and the inheritance of these alleles was investigated. Sixty patients with inflammatory bowel disease following a standardised dose escalation schedule of azathioprine or 6-mercaptopurine were closely monitored over the course of 20 weeks. During treatment, the TPMT gene expression decreased. In contrast, TPMT enzyme activity did not change. TPMT heterozygous patients had a lower probability of remaining in the 20week study. Forty-five percent of the patients were withdrawn due to adverse events, but 67% of these tolerated a lower dose of thiopurines. The inosine triphosphate pyrophosphatase polymorphism (ITPA 94C>A) was not associated with occurrences of adverse events

Interconnections between apoptotic and autophagic pathways during thiopurine-induced toxicity in cancer cells: the role of reactive oxygen species

Thiopurines (azathioprine, 6-mercaptopurine and 6-thioguanine) are a class of genotoxic drugs extensively used in the treatment of various illnesses including leukemia. Their underlying molecular mechanism of action involves the activation of apoptosis and autophagy but remains widely unclear. Here we present evidence that autophagy induction by thiopurines is a survival mechanism that antagonizes apoptosis and is involved in degrading damaged mitochondria through mitophagy. On the other hand, apoptosis is the main cell death mechanism by thiopurines as its inhibition prohibited cell death. Thus a tight interplay between apoptosis and autophagy controls cell fate in response to thiopurine treatment. Moreover, thiopurines disrupt mitochondrial function and induce a loss of the mitochondrial transmembrane potential. The involvement of the mitochondrial pathway in thiopurine-induced apoptosis was further confirmed by increased formation of reactive oxygen species (ROS). Inhibiting oxidative stress protected the cells from thiopurine-induced cell death and ROS scavenging prohibited autophagy induction by thiopurines. Our data indicate that the anticarcinogenic effects of thiopurines are mediated by complex interplay between cellular mechanisms governing redox homeostasis, apoptosis and autophagy.Funding Agencies|Swedish Childhood Cancer Foundation; Medical Research Council of Southeast Sweden</p

A skewed thiopurine metabolism is a common clinical phenomenon that can be successfully managed with a combination of low-dose azathioprine and allopurinol

Background and aims: A skewed thiopurine metabolism is a phenomenon associated with both poor treatment response and toxicity. Our aim was to evaluate the frequency of this phenomenon and the relationship to thiopurine methyltransferase (TPMT) function. Methods: All thiopurine metabolite measurements in adult patients (n=4033) between January 2006 and April 2012 were assessed to evaluate the occurrence of a skewed metabolism and the relationship to TPMT genotype and activity. Results: A skewed metabolism was observed in 14% of all patients. It only developed in patients with a normal TPMT genotype, but was observed at all TPMT activity levels within the normal range (9.1-24.2 U/ml RBC). Two cases that illustrate typical clinical scenarios of a skewed metabolism and the effect of combination treatment with low-dose azathioprine and allopurinol are presented. Conclusions: A skewed metabolism is a common clinical phenomenon in patients with a normal TPMT function, which can develop at all TPMT activity levels within the normal range. We suggest that metabolite measurements should be considered in patients not responding to treatment and in those with hepatotoxicity or myelotoxicity in order to detect a skewed metabolism, since this phenomenon can be successfully managed by a combination of low-dose azathioprine and allopurinol. (C) 2012 European Crohn's and Colitis Organisation. Published by Elsevier B.V. All rights reserved

Characterization of a novel sequence variant, TPMT*28, in the human thiopurine methyltransferase gene

Background The activity of the human enzyme thiopurine methyltransferase (TPMT) varies greatly between individuals because of genetic polymorphism. TPMT is involved in the detoxification and activation of thiopurines such as 6-mercaptopurine, 6-thioguanine, and azathioprine. These drugs are used in the treatment of acute lymphoblastic leukemia and inflammatory bowel disease. A total of 29 sequence variants have been identified so far in the TPMT gene. However, most of these variants are rare and not fully characterized. Methods and results In this study, we describe the identification and characterization of a novel TPMT sequence variant, originally found in a Swedish man of Italian origin. Sequencing of the variable number tandem repeats region of the TPMT promoter and exons III-X revealed a T-to-C transition at nucleotide 611, causing an amino acid substitution from isoleucine to threonine at amino acid 204, positioned in an alpha-helix, approximately 16A from the active site. This new variant was found in the patient and in his son. Both had intermediate enzyme activity (8.1 U/ml packed red blood cells and 8.8 U/ml packed red blood cells, respectively) and neither carried other variants in the coding region of the gene. To be able to study this variant in more detail, the TPMT*28 variant was expressed in Escherichia coli, and an in-vitro characterization of the variant revealed that the protein was destabilized and showed a stronger tendency towards degradation at 37 degrees C than the wild-type protein. The individuals carrying the TPMT*28 variant had less TPMT protein and lower TPMT activity in both red and white blood cells compared with a wild-type control. Conclusions We present a detailed in-vivo and in-vitro characterization of a novel TPMT sequence variant (TPMT*28) causing decreased TPMT activity. Individuals carrying TPMT*28 might have an increased risk for developing severe side effects if treated with conventional doses of thiopurines. Pharmacogenetics and Genomics 20: 700-707 (C) 2010 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins

Methotrexate binds to recombinant thiopurine S-methyltransferase and inhibits enzyme activity after high-dose infusions in childhood leukaemia

Purpose Important drugs in the treatment of childhood acute lymphoblastic leukaemia (ALL) are 6-mercaptopurine (6-MP) and methotrexate (MTX). Thiopurine methyltransferase (TPMT) is a polymorphic enzyme causing variability in 6-MP response and toxicity. The aim of this study was to investigate the fluctuation in TPMT enzyme activity over time and the effect of high-dose MTX infusions on TPMT enzyme activity and 6-MP metabolites in paediatric ALL patients. Methods Fifty-three children with ALL treated according to the NOPHO-ALL 2000 protocol were included in the study. TPMT enzyme activity was measured at six different times starting from diagnosis until after the end of maintenance treatment. TPMT and 6-MP metabolites were measured before the initiation of high-dose MTX (HD-MTX) infusions and at 66 h post-infusion. The interaction between MTX and TPMT was investigated in vitro using recombinant TPMT protein and a leukaemic cell line. Results Forty percent of TPMT wild-type individuals had deceptively low TPMT enzyme activity according to genotype at the time of diagnosis. TPMT activity had decreased significantly 66 h after the start of HD-MTX infusions (−9.2 %; p = 0.013). MTX bound to recombinant TPMT protein severely inhibiting TPMT enzyme activity (remaining activity 16 %). Conclusions Our results show that TPMT genotyping should be performed in children with ALL, since 40 % of the children in our study who carried the wild-type TPMT gene were at risk of initial underdosing of 6-MP in cases where only TPMT enzyme activity was determined. MTX inhibits the TPMT enzyme activity after HD-MTX infusions due to protein binding

Genetic Sequence Variants in TLR4, MBL or IL-1 Receptor Antagonist is not Associated to Increased Risk for Febrile Neutropenia in Children with ALL

Sequence variants in genes involved in the immune system have previously been linked to neutropenia as well as infections in cancer patients. Sequence variants in genes coding for TLR4, MBL, and IL-1Ra were investigated in relation to clinical utility of identifying severe episodes of febrile neutropenia (FN) in a cohort of children undergoing treatment for acute lymphoblastic leukemia. The study included 122 children, where data on FN and microbiological findings were retrospectively collected from medical records. Sequence variants in genes coding for MBL, TLR4, and IL-1Ra were identified by pyrosequencing, TaqMan SNP genotyping assay, and gel electrophoresis. A total of 380 episodes of FN were identified and in 139 episodes, there was a microbiological defined infection. Age and treatment intensity were all associated with the risk of developing FN. No sequence variant was associated to increased numbers of FN episodes. Two sequence variants in the TLR4 gene increased the risk of viral infection, whilst sequence variants in the IL-1Ra gene were associated to a decreased risk of bacterial blood-stream infection (BSI). The investigated sequence variants did not associate with increased risk for FN or to severe infections, as to why the clinical utility as a risk-stratification tool is low. Most episodes of FN were classified as fever with unknown origin, emphasizing the need for improved microbial detection methods.Funding Agencies|Swedish Childhood Cancer Foundation; Swedish Society of Medicine</p