Diagnostics and Model Selection for Generalized Linear Models and Generalized Estimating Equations

The use of generalized linear models and generalized estimating equations in the public health and medical fields are important tools for research, specifically for modeling clinical trials, evaluating preventive measures, and secondary data analysis. It is important for these researchers to have the necessary tools to analyze and model their data correctly. This dissertation focuses on a penalized maximum likelihood estimation method for generalized linear models, measures of association such as the coefficient of determination and R2 for generalized estimating equations, and a modified quasi-likelihood information criterion for generalized estimation equations. Common problems that arise during estimation of generalized linear models are bias of the estimates, small sample size, or complete or quasi-complete separation of data points. To address these problems, the first part of this dissertation introduces a penalized maximum likelihood approach that includes a penalty term directly in the score function prior to maximization of the likelihood, and then implements this method into statistical software. Generalized estimating equations are also an innovative way to model the within group correlation for longitudinal, clustered, or panel data. Currently, not many diagnostic statistics are available for these models. In the second part of this dissertation, we propose an R2 and several pseudo-R2 measures that help researchers with variable selection and provide a goodness of fit measure for the selected model. These calculations are also made accessible to researchers in statistical software. Generalized estimating equations are an extension to the generalized linear model specifically designed to address the within group correlation. To model the within group correlation in generalized estimating equations, the researcher must select the working correlation structure. However, the current quasi-likelihood information criterion for selecting the working correlation structure is not efficient in that it tends to favor the independent structure which assumes there is no within group correlation. In the last part of this dissertation, we propose a modified quasi-likelihood information criterion that outperforms the current quasi-likelihood information criterion in that this criterion favors the correct structure a large majority of the time. The efficiency of the estimates are improved when using the modified quasi-likelihood information criterion

Reproductive Efficiency of Captive Chinese- and Indian-Origin Rhesus Macaque (Macaca mulatta) Females

Reproductive and survival records (n = 2,913) from 313 Chinese-origin and 365 Indian-derived rhesus macaques at the Tulane National Primate Research Center (TNPRC) spanning three generations were studied. Least-squares analysis of variance procedures were used to compare reproductive and infant survival traits while proportional hazards regression procedures were used to study female age at death, number of infants born per female, and time from last birth to death. Chinese females were older at first parturition than Indian females because they were older when placed with males, but the two subspecies had similar first postpartum birth interval (1st PPBI) and lifetime postpartum birth interval (LPPBI). Females that gave birth to stillborn infants had shorter first postpartum birth intervals (1st PPBI) than females giving birth to live infants. Postpartum birth intervals decreased in females from age 3 to 12 but then increased again with advancing age. Chinese infants had a greater survival rate than Indian infants at 30 days, 6 months, and 1 year of age. Five hundred and forty-three females (80.01%) had uncensored, or true records for age at death, number of infants born per female, and time from the birth until death whereas 135 females (19.91%) had censored records for these traits. Low- and high-uncensored observations for age at death were 3 and 26 years for Chinese, and 3 and 23 years for Indian females. Uncensored number of infants born per female ranged from 1 to 15 for Chinese females and 1 to 18 for Indian females. Each of these traits was significantly influenced by the origin × generation interaction in the proportional hazards regression analyses, indicating that probabilities associated with age at death, number of infants born per female, and time from last birth to death for Chinese and Indian females did not rank the same across generations. © 2011 Wiley-Liss, Inc

Impact of a community-based approach to patient engagement in rural low-income adults with type 2 diabetes

"Community approaches to diabetes management are gaining empirical evidence for improving health outcomes (1,2). The Patient Activation Measure (PAM) has been utilized for predicting health outcomes. Individuals with higher levels of patient activation are more likely to have lower health care costs and obtain recommended diabetes preventive services (3). The purpose of this secondary data analysis was to explore the relationships between PAM scores, use of health services and HgA1C from a community-based intervention feasibility study for high-risk, rural dwelling adults with diabetes."--Introduction

Exploring information technology (IT) sophistication in New South Wales residential aged care facilities

The aim of this study was to determine baseline information technology (IT) sophistication in New South Wales (NSW), Australia, residential aged care facilities. Method: IT sophistication measures IT capabilities, extent of IT use and IT integration in two domains, resident care and clinical support. A survey was administered to all NSW residential aged care facilities (n = 876) between February and May 2017. A 15% response rate was achieved (130/876). Facilities were organised by organisational type, total residential places and remoteness. Using post-stratification weights, estimates of IT sophistication scores for NSW were determined. Regression was used to examine whether there was a linear relationship between IT sophistication and the ratio of residents receiving high care. Results: Participating facilities were similar to other NSW facilities in residential places and remoteness, but different in organisational type. IT sophistication was highest in IT capabilities and integration in resident care. IT sophistication was lowest in clinical support. Respondents had a mean of 1.2 years of IT experience. IT sophistication varied among aged care facilities. There was a linear relationship (P < 0.05) with the proportion of high-care residents and total IT sophistication Conclusion: Routine reports of IT sophistication in aged care are not available. If data were available, determining the influence of IT sophistication on the quality care for residential aged care would be possible. What is known about the topic?: Aged care settings that deliver care to the older population need to be contemporary in their approach to delivering high-quality and safe care. Health IT holds great potential for improving the quality and safety of care of older residents in aged care facilities. What does this paper add?: This report provides a baseline assessment of IT capabilities, extent of IT use and IT integration, called IT sophistication, among aged care facilities with variable characteristics. What are implications for practitioners?: Increasing IT sophistication has the potential to improve the quality of care delivered by aged care staff

PD-L1 Expression with Epithelial Mesenchymal Transition of Circulating Tumor Cells Is Associated with Poor Survival in Curatively Resected Non-Small Cell Lung Cancer

In addition to the FDA-approved definition of a circulating tumor cell (CTC), various CTC phenotypes have been discovered. Epithelial-mesenchymal transition (EMT) of cancer cells is directly linked to PD-L1 upregulation. The goal of the study was to investigate PD-L1 expression and EMT in CTCs of non-small cell lung cancer (NSCLC) patients, and perform an outcome analysis. Prospectively, 7.5 mL peripheral blood was collected from 30 NSCLC patients that underwent surgery and 15 healthy controls. CTCs were enriched by size-based microfilter and immunofluorescence stainings performed (cytokeratin (CK) 8/18/19, EpCAM, CD45, PD-L1, EMT markers vimentin, and N-Cadherin, DAPI). Patient-matched NSCLC tissues were also stained. CTC staining intensity was quantified with a software and correlated with patient-matched NSCLC tissues and survival. PD-L1 and EMT markers were expressed at significantly higher proportions in CTCs than patient-matched NSCLC tissues (p &lt; 0.05); &ge;3 PD-L1pos/EMTposCTCs were associated with significantly poorer survival after curative surgery (p &lt; 0.05). No CTCs were detected in 15 healthy controls. This study shows that PD-L1 expression and EMT of CTCs is a negative survival predictor for NSCLC patients. The therapeutic role of the molecular linkage of PD-L1 and EMT will need to be further investigated, as linked pathways could be targeted to improve NSCLC outcome