A computationally efficient bootstrap-equivalent test for ANOVA in skewed populations with a large number of factor levels

Doctor of PhilosophyDepartment of StatisticsHaiyan WangAdvances in technology easily collect a large amount of data in scientific research such as agricultural screening and micro-array experiments. We are particularly interested in data from one-way and crossed two-way designs that have a large number of treatment combinations but small replications with heteroscedastic variances. In this framework, several test statistics have been proposed in the literature. Even though the form of these proposed test statistics may be different, they all use limiting normal or chi-square distribution to conduct their tests. Such approximation approaches the true distribution very slowly when the sample size ni is small while the number of levels of treatments a gets large. A strategy to obtain better accuracy in the classical large sample size setting is to use the bootstrap procedure with studentized statistic. Unfortunately, the available bootstrap method fails when the number of treatment level combinations is large while the number of replications is small. The Fisher and Hall (1990) asymptotic pivotal statistic under large sample size setting is no longer pivotal under small sample size setting with large number of treatment levels. In the first part of this dissertation, we start with describing suitable bootstrap statistics and procedures for hypothesis tests in one- and two-way ANOVA with a large number of levels and small sample sizes. We prove that the theoretical type I error-rate of Akritas and Papadatos (2004) and Wang and Akritas (2006) test statistics and their corresponding bootstrap versions have accuracy of order O(1/√a). We then modify their statistics to obtain asymptotically pivotal statistics in our current framework. We prove that the theoretical type I error-rate of the bootstrap version of the pivotal statistics is accurate up to order O(1/√a). In the second part of the dissertation, we propose a new test statistic in one-way ANOVA which is asymptotically pivotal in the current setting. We improve the accuracy of approximation of the distribution of the test statistic by deriving asymptotic expansion of the statistic under the current framework and define a new test rejection region through Cornish-Fisher expansion of quantiles. The type I error-rate of the new test has a faster convergence rate and is accurate up to order O(1/a). Simulation studies show that our tests performs better in terms of type I error-rate but comparable power with that of Akritas and Papadatos (2004) in the large a small ni setting. The connection between our asymptotic expansions and bootstrap distribution in the large a small ni setting is discussed. Our proposed test based on asymptotic expansion and Cornish-Fisher expansion of quantiles have both the advantage of higher accuracy and computational efficiency due to no resampling is needed

Vitamin B-12 deficiency in type 2 diabetic patients on metformin: a cross-sectional study from South-Western part of Ghana

Introduction: Metformin is the most widely administered anti-diabetic medication among type 2 diabetes mellitus (T2DM) patients. However, metformin induces vitamin B12 malabsorption which may increase the risk of vitamin B12 deficiency among T2DM patients. We determined the prevalence of vitamin B12 deficiency and related risk factors among Ghanaian T2DM patients on metformin therapy. Methods: This cross-sectional study recruited 196 T2DM patients attending the outpatient diabetic clinic at the Effia Nkwanta Regional Hospital, Ghana. Fasting venous blood was collected for biochemical analysis. Vitamin B12 deficiency was defined as serum B12 \u3c 100 pg/ml and methylmalonic acid (MMA) ≥ 0.4µmol/L. Results: The prevalence of vitamin B12 deficiency based on serum vitamin B12, MMA, and the combination of both methods were 32.1%, 14.8%, and 14.3%, respectively. Longer duration of metformin use [5-9 years, aOR= 2.83, 95% CI (1.03-7.81), p=0.045 and ≥ 10 years, aOR= 4.17, 95% CI (1.41-12.33), p=0.010], higher daily dose of metformin [1000-2000 mg/day, aOR= 1.34, 95% CI (0.25-2.74), p=0.038 and \u3e 2000 mg/day, aOR= 1.13, 95% CI (0.39-2.97), p=0.047], and very high body fat [aOR= 2.98, 95% CI (1.47-6.05), p=0.020] were significantly associated with increased odds of vitamin B12 deficiency. For daily dose of metformin, a cutoff value of 1500 mg/day presented with a sensitivity, specificity, and AUC of 71.4%, 40.1%, and 0.54 (95% CI, 0.53-0.54), respectively, in predicting vitamin B12 deficiency. A ≥ six (6) years duration of metformin therapy presented with a sensitivity, specificity, and AUC of 70.4%, 62.9%, and 0.66 (95% CI, 0.57-0.75), respectively, in predicting vitamin B12 deficiency. Conclusion: Vitamin B12 deficiency is high among T2DM patients on metformin therapy in Ghana. There is the need for regular monitoring of vitamin B12 levels especially in T2DM patients on metformin daily dose of ≥ 1500 mg for duration of therapy ≥ 6 years

Overview of preparedness and response to COVID-19 in Ghana

The Coronavirus disease 2019 (COVID-19) outbreak in Ghana is part of an ongoing pandemic caused by the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2). The first two cases of COVID-19 were confirmed in Ghana on 12th March 2020. COVID-19 was consequently declared a Public Health Emergency of National Concern, triggering several response actions, including enhanced surveillance, case detection, case management and contact tracing, closure of borders, suspension of international flights, ban on social gatherings and closure of schools. Preparedness and response plans were activated for implementation at the national, regional, district and community levels. Ghana’s Strategic approaches were to limit and stop the importation of cases; detect and contain cases early; expand infrastructure, logistics and capacity to provide quality healthcare for the sick; minimise disruption to social and economic life and increase the domestic capacity of all sectors to deal with existing and future shocks. The health sector strategic frame focused on testing, treatment, and tracking. As of 31st December 2020, a total of 535,168 cases, including 335 deaths (CFR: 0.61%), have been confirmed with 53,928 recoveries and 905 active cases. All the regions have reported cases, with Greater Accra reporting the highest number. The response actions in Ghana have seen highlevel political commitment, appropriate and timely decisions, and a careful balance of public health interventions with economic and socio-cultural dynamics. Efforts are ongoing to intensify non-pharmaceutical interventions, sustain the gains made so far and introduce COVID-19 vaccines to reduce the public health burden of the disease in Ghan

The role of digital surveillance during outbreaks: the Ghana experience from COVID‑19 response

Over the years, Ghana has made notable strides in adopting digital approaches to address societal challenges and meet demands. While the health sector, particularly the disease surveillance structure, has embraced digitization to enhance case detection, reporting, analysis, and information dissemination, critical aspects remain to be addressed. Although the Integrated Disease Surveillance and Response (IDSR) structure has experienced remarkable growth in digitization, certain areas require further attention as was observed during the COVID-19 pandemic. Ghana during the COVID-19 pandemic, recognized the importance of leveraging digital technologies to bolster the public health response. To this end, Ghana implemented various digital surveillance tools to combat the pandemic. These included the “Surveillance Outbreak Response Management and Analysis System (SORMAS)”, the digitalized health declaration form, ArcGIS Survey123, Talkwalker, “Lightwave Health information Management System” (LHIMS), and the “District Health Information Management System (DHIMS)”. These digital systems significantly contributed to the country's success in responding to the COVID-19 pandemic. One key area where digital systems have proved invaluable is in the timely production of daily COVID-19 situational updates. This task would have been arduous and delayed if reliant solely on paper-based forms, which hinder efficient reporting to other levels within the health system. By adopting these digital systems, Ghana has been able to overcome such challenges and provide up-to-date information for making informed public health decisions. This paper attempts to provide an extensive description of the digital systems currently employed to enhance Ghana's paper-based disease surveillance system in the context of its response to COVID-19. The article explores the strengths and challenges or limitations associated with these digital systems for responding to outbreaks, offering valuable lessons that can be learned from their implementation

Embedding research for innovation to meet societal needs in national research systems : Experiences from Ghana

The experiences synthesised in this article indicate how significant effects in two agricultural domains have been achieved by creating pathways for inter-dependent socio-technical and institutional changes, at a range of levels of action, governance and policy-making. The synthesis emphasizes the importance of co-learning, experimentation, and critical reflection among a wide network of 'champions' of transformational change on behalf of smallholder farmers and processors. It shows that innovation processes may involve actors along entire value chains, industry leaders at national level, or local level actors seeking to widen the space for change beyond their immediate circle of direct influence. While the research and development initiatives of the domains are shown to have been critical in identifying the constraints and opportunities of smallholders, and also to the effects documented, this was largely because the research effort converged around empirically grounded problems and opportunities identified. The information sought, and the solutions found useful, were determined by the members of innovation platforms that drove the processes of change.</p

Increased insulin resistance with reduced beta cell function in recovered COVID-19 Ghanaians

Aim: This study compares levels of insulin resistance and beta-cell function and their relationship with liver enzymes in recovered COVID-19 participants and their uninfected counterparts in a cross-sectional study design in the Tamale metropolis of Ghana. Methods: Biochemical indices for liver function, lipid metabolism, inflammation and oxidative stress were assessed under fasting state in 110 recovered COVID-19 and 116 uninfected participants. The homeostatic model assessment of insulin resistance (HOMA-IR) and the triglyceride-glucose index (TyG) were employed for the assessment of insulin resistance. Results: Recovered COVID-19 participants presented lower (P  0.05) between the study groups. Prevalence of insulin resistance ranged from 61 % (71/116) to 81 % (89/110) for the uninfected and recovered COVID-19 participants respectively. Selected liver enzymes associated with HOMA-IR and TyG. Conclusion: The risk of developing type 2 diabetes mellitus appears higher in recovered COVID-19 participants than their uninfected counterparts despite the high prevalence of insulin resistance in both groups

Access and Control of Resources and Participation in Rice-Breeding Activities among Men and Women Farmers in Southern Ghana

This paper provides evidence of gender differences in the access and control of resources and their relation to participation in rice-breeding activities among men and women farmers in southern Ghana. We used a mixed methods design which involved the use of qualitative data collected through focus group discussions (FGDs) and key informant interviews (KIIs) and quantitative data collection through a survey. Using data collected from 315 smallholder rice farmers, perception analyses and probit and multivariate regression were employed in the analyses. Our findings indicate that higher levels of education, experience in rice farming, a favorable dependency ratio, larger farm size, more rice plots, access to extension services, and involvement with financial organizations positively influence participation in rice-breeding activities. On the other hand, distance to market is found to have a negative impact on participation. Moreover, years of education, experience in rice farming, farm size, number of rice plots, dependency ratio, and distance to market were found to negatively influence the control of production resources among both male and female participants in rice-breeding activities. From both the quantitative and qualitative results, men had more access to productive resources than women. Insights from this study will enhance gender equity in promoting the participation of both men and women in rice varietal development activities

An exploratory pharmacogenetic screening of SLC22A6, SLC22A8, ABCC4 and ABCC10 genes in a cohort of Ghanaian HBV patients

Abstract Background Organic anion transporters and efflux transporters are involved in the metabolism of drugs such as tenofovir disoproxil fumarate (TDF). Given the important role of organic anions and efflux transporters in drug disposition, genetic variations lead to interindividual differences in drug response. Variations in the SLC and ABC transporters have been associated with drug-induced renal dysfunction. Looking at the prevalence of HBV infection in our population and the use of drugs such as TDF in managing this condition, this study aimed to undertake an exploratory analysis of genetic variation in renal transporters SLC22A6, SLC22A8, ABCC10 and ABCC4 in a Ghanaian HBV infected cohort. Methods We genotyped 160 HBV infected patients for SNPs in SLC22A6 (rs12293966, rs4149170, rs6591722, rs955434), SLC22A8 (rs11568487), ABCC10 (rs700008, rs831311) and ABCC4 (rs9282570) genes. Clinicodemographic data was taken, and glomerular filtration rate (eGFR) was estimated using the CKD-EPI formula. Genotyping was undertaken using Iplex gold SNP genotyping protocol on the Agena MassARRAY® system. Statistical analysis was undertaken using packages in Stata SE (v17) and GraphPad prism. Hardy–Weinberg equilibrium, haplotype inference, and linkage disequilibrium (LD) were evaluated using web-based tools LDlink and Shesis. Results The average eGFR was 79.78 ± 33.08 mL/min/1.73 m2 with 31% classified as stage 1 with normal or high GFR (eGFR > 90 mL/min/1.73 m2) and 45% with stage 2 CKD (> 60–89.99 mL/min/1.73 m2). All variants were in HWE except rs4149170, rs9282570 and rs700008 where p < 0.05. Strong LD was observed in the variants rs6591722, rs4149170, rs12293966, rs955434 and rs11568487. There was significant association between rs12293966 and eGFR stage under crude dominant inheritance model (OR 0.27, 95% CI 0.08–0.81; p = 0.019). Under crude model (OR 0.21, 95% CI 0.07–0.66; p = 0.008), adjusted model 1 (OR 76, 95% CI 0.39–7.89; p = 0.014) and adjusted model 2 (OR 0.30, 95% CI 0.12–0.78; p = 0.013) there was significant association observed between rs12293966 and eGFR stage in a codominant inheritance. Conclusion The associations observed in this study point to the need for further evaluation with the population of HBV patients on TDF treatment in addition to other factors that would lead to unfavorable outcomes. This exploratory finding may require confirmation in a larger cohort with proper phenotyping to investigate the exact pharmacogenetic mechanisms

Knowledge Level and Determinants of Neonatal Jaundice: A Cross-Sectional Study in the Effutu Municipality of Ghana

Background. Neonatal jaundice (NNJ) is a major cause of hospital admission during the neonatal period and is associated with significant mortality. This case-control study with cross-sectional design sought to identify the possible factors associated with neonatal jaundice and assess maternal knowledge level of this condition. Methods. One hundred and fifty (150) neonates comprising 100 with clinically evident jaundice and 50 without jaundice were conveniently recruited from the Trauma and Specialist Hospital in the Effutu Municipality. Blood samples were collected for the determination of serum bilirubin, glucose-6-phosphate dehydrogenase (G6PD), status and blood group (ABO and Rhesus). Well-structured questionnaire was used to collect maternal and neonate sociodemographic and clinical history. Results. Majority (54%) of neonates developed jaundice within 1–3 days after birth with 10% having it at birth. Duration of labour and neonatal birth weight were associated with neonatal jaundice (P<0.05). G6PD abnormality was found in 11 (12%) of the neonates with jaundice and ABO incompatibility was present in 18%. Neonates delivered by mothers with formal occupation and those who had prolonged duration of labour were significantly more likely to have neonatal jaundice (OR = 4.174, P=0.003; OR = 2.389, P=0.025, resp.). Neonates with low birth weight were also more likely to develop neonatal jaundice (OR = 2.347, P=0.044). Only 17.3% of mothers had heard of neonatal jaundice. School was the major source of information on neonatal jaundice (34.6%). Majority of participants (mothers) did not know that NNJ can cause damage to other organs in the body (90%). Conclusion. Low neonatal birth weight and prolonged duration of labour are associated with neonatal jaundice. Mothers had inadequate knowledge of neonatal jaundice and its causes