Design and analysis for three level hierarchical structures with count response

In numerous intervention studies and education field trials, random assignment to treatment occurs in clusters rather than at the level of observation. This departure of random assignment of units may be due to logistics, political feasibility, or ecological validity. Data within the same cluster or grouping are often correlated. Application of traditional regression techniques, which assume independence between observations, to clustered data produce consistent parameter estimates. However such estimators are often inefficient as compared to methods which incorporate the clustered nature of the data into the estimation procedure (Neuhaus 1993).1 Multilevel models, also known as random effects or random components models, can be used to account for the clustering of data by estimating higher level, or group, as well as lower level, or individual variation. Designing a study, in which the unit of observation is nested within higher level groupings, requires the determination of sample sizes at each level. This study investigates the design and analysis of various sampling strategies for a 3-level repeated measures design on the parameter estimates when the outcome variable of interest follows a Poisson distribution. ^ Results study suggest that second order PQL estimation produces the least biased estimates in the 3-level multilevel Poisson model followed by first order PQL and then second and first order MQL. The MQL estimates of both fixed and random parameters are generally satisfactory when the level 2 and level 3 variation is less than 0.10. However, as the higher level error variance increases, the MQL estimates become increasingly biased. If convergence of the estimation algorithm is not obtained by PQL procedure and higher level error variance is large, the estimates may be significantly biased. In this case bias correction techniques such as bootstrapping should be considered as an alternative procedure. For larger sample sizes, those structures with 20 or more units sampled at levels with normally distributed random errors produced more stable estimates with less sampling variance than structures with an increased number of level 1 units. For small sample sizes, sampling fewer units at the level with Poisson variation produces less sampling variation, however this criterion is no longer important when sample sizes are large. ^ 1Neuhaus J (1993). “Estimation efficiency and Tests of Covariate Effects with Clustered Binary Data”. Biometrics , 49, 989–996^

Molecular mechanisms of prostatic carcinoma growth and progression

Prostate cancer represents the most commonly diagnosed malignancies in American men and is the second leading cause of male cancer deaths. The overall objectives of this research were designed to understand the cellular and molecular mechanisms of prostatic carcinoma growth and progression. This dissertation was divided into two major parts: (1) to clone and characterize soluble factor(s) associated with bone that may mediate prostatic carcinoma growth and progression; (2) to investigate the roles of extracellular matrix in prostatic carcinogenesis.^ The propensity of prostate cancer cells to metastasize to the axial skeleton and the subsequent osteoblastic reactions observed in the bone indicate the possible reciprocal cellular interaction between prostate cancer cells and the bone microenvironment. To understand the molecular and cellular basis of this interaction, I focused on the identification and cloning of soluble factor(s) from bone stromal cells that may exert direct mitogenic action on cultured prostate cells. A novel BPGF-1 gene expressed specifically by bone and male accessory sex organs (prostate, seminal vesicles, and coagulating gland) was identified and cloned.^ The BPGF-1 was identified and cloned from a cDNA expression library prepared from a human bone stromal cell line, MS. The conditioned medium (CM) of this cell line contains mitogenic materials that induce human prostate cancer cell growth both in vivo and in vitro. The cDNA expression library was screened by an antibody prepared against the mitogenic fraction of the CM.^ The cloned BPGF-1 cDNA comprises 3171 nucleotides with a single open reading frame of 1620 nucleotides encoding 540 amino acids. The BPGF-1 gene encodes two transcripts (3.3 and 2.5 kb) with approximately equal intensity in human cells and tissues, but only one transcript (2.5 kb) in rat and mouse tissues. Southern blot analysis of human genomic DNA revealed a single BPGF-1 gene. The BPGF-1 gene is expressed predominantly in bone and seminal vesicles, but at a substantially lower level in prostate. Polyclonal antibodies generated from synthetic peptides that correspond to the nucleotide sequences of the cloned BPGF-1 cDNA reacted with a putative BPGF-1 protein with an apparent molecular weight of 70 kDa. The conditioned media isolated from COS cells transfected with BPGF-1 cDNA stimulated the proliferation and increased the anchorage-independent growth of prostate epithelial cells. These findings led us to hypothesize that BPGF-1 expression in relevant organs, such as prostate, seminal vesicles, and bone, may lead to local prostate cancer growth, metastasis to the seminal vesicles, and subsequently dissemination to the skeleton.^ To assess the importance of extracellular matrix in prostatic carcinogenesis, the role of extracellular matrix in induction of rat prostatic carcinoma growth in vivo was evaluated. NbE-1, a nontumorigenic rat prostatic epithelial cell line, was induced to form carcinoma in athymic nude hosts by coinjecting them with Matrigel and selected extracellular matrix components. Induction of prostatic tumor formation by laminin and collagen IV was inhibited by their respective antibodies. Prostatic epithelial cells cloned from the tumor tissues were found to form tumors in athymic nude hosts in the absence of exogenously added extracellular matrix. These results suggest that extracellular matrix induce irreversibly prostatic epithelial cells that behave distinctively different from the parental prostatic epithelial cell line. ^

Evaluation of the accuracy of multilevel analysis parameter estimates for intra-cluster correlation in correlated binary data

Many studies in biostatistics deal with binary data. Some of these studies involve correlated observations, which can complicate the analysis of the resulting data. Studies of this kind typically arise when a high degree of commonality exists between test subjects. If there exists a natural hierarchy in the data, multilevel analysis is an appropriate tool for the analysis. Two examples are the measurements on identical twins, or the study of symmetrical organs or appendages such as in the case of ophthalmic studies. Although this type of matching appears ideal for the purposes of comparison, analysis of the resulting data while ignoring the effect of intra-cluster correlation has been shown to produce biased results.^ This paper will explore the use of multilevel modeling of simulated binary data with predetermined levels of correlation. Data will be generated using the Beta-Binomial method with varying degrees of correlation between the lower level observations. The data will be analyzed using the multilevel software package MlwiN (Woodhouse, et al, 1995). Comparisons between the specified intra-cluster correlation of these data and the estimated correlations, using multilevel analysis, will be used to examine the accuracy of this technique in analyzing this type of data. ^

THE EFFECT OF FAMILY ENVIRONMENT FACTORS IN THE ETIOLOGY OF CHILD ABUSE

Twenty-three abusing couples were compared with a matched group of 23 non-abusing couples in terms of stress levels and family environment factors (cohesion, expressiveness, conflict, independence, achievement orientation, organization, control) which might mediate the response of abuse to stress. Parents who had physically abused their children were found to have significantly greater stress, conflict, and control and a significantly lower level of cohesion, independence, and achievement orientation than non-abusing parents. However, none of the mediating effects of the family environment factors reached the level of significance. ^

Mexican Americans' awareness, knowledge, and beliefs of hypertension

Cardiovascular disease (CVD) is the number one cause of death for people in Texas as well as Mexico. The progressive morbidity and mortality of CVD can be prevented initially and controlled through regular health screenings or visits to the physician where health markers such as hypertension can be detected and treated. Yet, many people go unaware of existing hypertension not only due to lack of access to health care but to their own personal beliefs, ideas, or perceived barriers that prevent them from seeking preventative health care. ^ The main purpose of this study was to evaluate whether individuals of Mexican origin, who have some form of medical coverage, posses more knowledge, more perceived severity, less perceived barriers, and greater self-efficacy in regards to hypertension than those individuals who have no medical coverage. This was done by addressing the following specific aims: 1.To evaluate the association between individuals who have health care coverage and those who do not have health care coverage in regards to their beliefs of hypertension; 2. To evaluate if there exists a variation among the respondents demographic data and their beliefs of hypertension. ^ The total number of respondents were 150; with 75 being from Cuidad Juarez, and 75 being from El Paso, Texas. The results indicated that the individuals with some form of medical coverage perceived themselves to be more susceptible to suffering a cardiac event or developing heart disease than those who had no form of medical coverage. The individuals with some form of health care coverage also found themselves having less perceived barriers than those who had no health care coverage. The level of education seemed to have some association with individuals perceiving themselves as being susceptible to experiencing a cardiac event if they do not control their hypertension. Regarding self-efficacy, or the self-reported confidence in performing certain behaviors to controlling hypertension, those individuals who perceived themselves as having no self-efficacy had a lower level of education, compared to those who did perceive themselves as possessing self-efficacy. The findings of this study indicate that beliefs regarding hypertension and medical coverage are variables that need to be investigated further for individuals in the El Paso and Cuidad Juarez region. ^

Investigation of I -compounds (newly discovered indigenous DNA modifications) by different approaches

I-compounds are newly discovered covalent DNA modifications detected by the $\sp{32}$P-postlabeling assay. They are age-dependent, tissue-specific and sex-different. The origin(s), chemistry and function(s) of I-compounds are unknown. The total level of I-compounds in 8-10 month old rat liver is 1 adduct in 10$\sp7$ nucleotides, which is not neglectable. It is proposed that I-compounds may play a role in spontaneous tumorigenesis and aging.^ In the present project, I-compounds were investigated by several different approaches. (1) Dietary modulation of I-compounds. (2) Comparison of I-compounds with persistent carcinogen DNA adducts and 5-methylcytosine. (3) Strain differences of I-compounds in relation to organ site spontaneous tumorigenesis. (4) Effects of nongenotoxic hepatocarcinogenes on I-compounds.^ It was demonstrated that the formation of I-compounds is diet-related. Rats fed natural ingredient diet exhibited more complex I-spot patterns and much higher levels than rats fed purified diet. Variation of major nutrients (carbohydrate, protein and fat) in the diet, produced quantitative differences in I-compounds of rat liver and kidney DNAs. Physiological level of vitamin E in the diet reduced intensity of one I-spot compared with vitamin E deficient diet. However, extremely high level of vitamin E in the diet gave extra spot and enhanced the intensities of some I-spots.^ In regenerating rat liver, I-compounds levels were reduced, as carcinogen DNA adducts, but not 5-methylcytosine, i.e. a normal DNA modification.^ Animals with higher incidences of spontaneous tumor or degenerative diseases tended to have a lower level of I-compounds.^ Choline devoid diet induced a drastic reduction of I-compound level in rat liver compared with choline supplemented diet. I-compound levels were reduced after multi-doses of carbon tetrachloride (CCl$\sb4$) exposure in rats and single dose exposure in mice. An inverse relationship was observed between I-compound level and DNA replication rate. CCl$\sb4$-related DNA adduct was detected in mice liver and intensities of some I-spots were enhanced 24 h after a single dose exposure.^ The mechanisms and explanations of these observations will be discussed. I-compounds are potentially useful indicators in carcinogenesis studies. ^

Patient Characteristics and Outcomes of Gastrointestinal Stromal Tumor Patients Undergoing Imatinib Plasma Level Testing

Although gastrointestinal stromal tumor (GIST) is effectively treated with imatinib, there are a number of clinical challenges in the optimal treatment of these patients. The plasma steady-state trough level of imatinib has been proposed to correlate with clinical outcome. Plasma imatinib level may be affected by a number of patient characteristics. Additionally, the ideal plasma trough concentration of imatinib is likely to vary based on the KIT genotype (genotype determines imatinib binding affinity) of the individual patient. Patients’ genotype or plasma imatinib level may influence the type and duration of response that is appreciable by clinical evaluation. The objectives of this study were to determine effects of genotype on the type of response appreciable by current imaging criteria, to determine the distribution of plasma imatinib levels in patients with GIST, to determine factors that correlate with plasma imatinib level, to determine the incremental effects of imatinib dose escalation; and to explore the median plasma levels and outcomes of patients with various KIT mutations. We therefore obtained KIT mutation information and analyzed CT response for size and density measurement of GISTs at baseline and within the first four moths of imatinib treatment. In 126 patients with metastatic/unresectable disease, the KIT genotype of patients’ tumor was significantly associated with unique response characteristics measurable by CT. Furthermore, hepatic and peritoneal metastases differed in their response characteristics. A subgroup of patients with KIT exon 9 mutation, who received higher doses of imatinib and experienced higher trough imatinib levels, experienced improved progression-free survival similar to that of KIT exon 11 patients. Therefore, we have found that imatinib plasma levels were higher in patients with elevated Aspartate amino transferase, were women, were older, or were being treated concomitantly with CYP450 substrate drugs. As expected, CYP450 inducers correlated with a lower plasma imatinib levels in GIST patients. Renal metabolism of imatinib accounts for <10%, so it was not included in the analysis but may affect covariates. Interestingly, there was a trend for low imatinib levels and inferior progression-free survival in patients who had undergone complete gastrectomy. Patients with KIT exon 9 mutation in our cohort received higher imatinib doses, experienced higher trough imatinib levels, and experienced a PFS similar to that of KIT exon 11 patients. In conclusion, imatinib plasma levels are influenced by a number of patient characteristics. The optimal imatinib plasma level for individual patients is not known but is an area of intense investigation. Our study confirms patients with KIT exon 9 mutations benefit from high-dose imatinib and higher trough imatinib levels.

An investigation of the association between obesity, acanthosis nigricans, and fasting serum insulin level in 6--9 year old children living on the El Paso-Juarez U.S.-Mexico border

The objectives of this study were to investigate the relationship between fasting serum insulin levels and Acanthosis Nigricans (AN) (a dermatological condition characterized by hyperpigmentation and thickening of the skin in specific body areas such as the neck and knuckles) and obesity among 6 to 9 year old children. Children were selected at random from a pediatric clinic located on the U.S.-Mexico border. Because none of the children participants had a weight for height at or above the 97th percentile of the CDC growth charts, obesity was defined as weight for height at or above the 95th percentile and at risk of overweight between the 85 th and 95th percentiles of the CDC growth charts. Anthropometrics, blood samples for fasting serum insulin and blood glucose, and a picture of the neck were obtained at baseline (n = 85) and 6 months later (n = 49). None of the children partipating had high fasting serum insulin levels and only 2 children had AN degree 2 (moderately severe). At baseline children with a weight for height at or above the 95th, percentile had 15 units less of insulin than children who weighed less. However, 6 months later this was not confirmed, thus the baseline result is considered to be an anomaly. Eventhough statistical significance was not reached, results showed that children without AN had 5 percentiles lower weight for height than children with AN. The most important recommendation from this study is the need to monitor longitudinal growth in children to characterize the individual child's growth pattern. AN seems to be related to longitudinal growth changes. ^

Trends in utilization of computer tomography (CT) scans for victims of motor vehicle collision (MVCs) in a level I trauma center from 1996 to 2006

Purpose. To evaluate trends in the utilization of head, abdominal, thoracic and other body regions CTs in the management of victims of MVC at a level I trauma center from 1996 to 2006.^ Method. From the trauma registry, I identified patients involved in MVC's in a level I trauma center and categorized them into three age groups of 13-18, 19-55 and ≥56. I used International Classification of Disease (ICD-9-CM) codes to find the type and number of CTs examinations performed for each patient. I plotted the mean number of CTs per patient against year of admission to find the crude estimate of change in utilization pattern for each type of CT. I used logistic regression to assess whether repetitive CTs (≥ 2) for head, abdomen, thorax and other body regions were associated with age group and year of admission for MVC patients. I adjusted the estimates for gender, ethnicity, insurance status, mechanism and severity of injury, intensive care unit admission status, patient disposition (dead or alive) and year of admission.^ Results. Utilization of head, abdominal, thoracic and other body regions CTs significantly increased over 11-year period. Utilization of head CT was greatest in the 13-18 age group, and increased from 0.58 CT/patient in 1996 to 1.37 CT/patient in 2006. Abdominal CTs were more common in the ≥56+ age group, and increased from 0.33 CT/patient in 1996 to 0.72 CT/patient in 2006. Utilization of thoracic CTs was higher in the 56+ age group, and increased from 0.01 CT/patient in 1996 to 0.42 CT/patient in 2006. Utilization of other CTs did not change materially during the study period for adolescents, adults or older adults. In the multivariable analysis, after adjustment for potential confounders, repetitive head CTs significantly increased in the 13-18 age group (95% CI: 1.29-1.87, p=<0.001) relative to the 19-55 age group. Repetitive thoracic CT use was lower in adolescents (95% CI: 0.22-0.70, p=<0.001) relative to the 19-55 age group.^ Conclusion. There has been a substantial increase in the utilization of head, abdominal, thoracic and other CTs in the management of MVC patients. Future studies need to identify if increased utilization of CTs have resulted in better health outcome for these patients. ^

Relationship between parental feeding practices and weight status in a lower socioeconomic pre-school population

High prevalence of overweight and obesity among preschool children in the low income population is consistently documented in research with one of every seven low-income, preschool-aged children classified as obese. Parental feeding practices have the potential to be contributing factors to the obesity epidemic. However, the impact of parental feeding practices on obesity in preschool age children has not been well explored. The purpose of this study was to determine relationships between the parental feeding practices of using dessert, sweets or candy as a reward for finishing foods, restricting dessert if the child does not finish their plate at dinner, asking the child to consume everything on their plate at dinner, and having family dinners to obesity in low income, preschool age children.^ A cross-sectional secondary data analysis was completed using the STATA 11 statistical software. Descriptive statistics were completed to summarize demographic and BMI data of participants, as well as parental feeding behavior variables. Pearson’s correlation was implemented to determine a correlation between parental feeding behavior variables and BMI z scores. Predictive relationships between the variables were explored through multivariable linear regression analysis. Regression analyses were also completed factoring in the confounders of gender, age, and ethnicity.^ Results revealed (1) no significant correlations or predictive trends between the use of rewards, forced consumption, or family dinner and BMI in low income preschool age children, and (2) a significant negative correlation and predictive trend between restriction of desserts and BMI in low income preschool age children. Since the analysis supported the null hypothesis for the practices of reward use, forced consumption, and family dinner, these practices are not considered risk factors for obese level BMIs. The inverse association found for practice of restriction and BMI suggests it is unnecessary to discourage parents from using restriction. Limitations of the study included the sample size, reliability of the answers provided on the Healthy Home Survey by participant guardians, and generalizability of the sample to the larger population.^

Confidential inquiry into perinatal mortality in the Lower Rio Grande Valley, 1988

A review of 1985 neonatal death statistics in the Lower Rio Grande Valley of Texas revealed an excessive perinatal death rate among Hispanics compared to Anglos. In order to identify factors contributing to perinatal mortality in the region and to determine if existing perinatal services were adequate, a confidential inquiry into each 1988 perinatal death was performed.^ Medical risk factors in the mothers were infrequent. The most commonly noted pregnancy complication was polyhydramnios. This complication is often associated with anencephalus which was the most frequent birth anomaly detected in the region.^ The study results did not reveal an association between lay midwife deliveries in the region and excessive perinatal mortality nor did perinatal mortality appear to be associated with a lack of neonatal intensive care facilities. Lack of prenatal care was the most commonly encountered preventable factor associated with perinatal death. It was not possible to determine if the level of care for Anglos and Hispanics differed because of the low number of Anglo deaths although the socioeconomic level of deaths in each of the ethnic groups was the same. ^

A COMPARISON OF NEONATAL MORTALITY BETWEEN HOSPITALS WITH LEVEL III NEWBORN INTENSIVE CARE UNITS AND ALL OTHER HOUSTON HOSPITALS

A number of medical and social developments have had an impact on the neonatal mortality over the past ten to 15 years in the United States. The purpose of this study was to examine one of these developments, Newborn Intensive Care Units (NICUs), and evaluate their impact on neonatal mortality in Houston, Texas.^ This study was unique in that it used as its data base matched birth and infant death records from two periods of time: 1958-1960 (before NICUs) and 1974-1976 (after NICUs). The neonatal mortality of single, live infants born to Houston resident mothers was compared for two groups: infants born in hospitals which developed NICUs and infants born in all other Houston hospitals. Neonatal mortality comparisons were made using the following birth-characteristic variables: birthweight, gestation, race, sex, maternal age, legitimacy, birth order and prenatal care.^ The results of the study showed that hospitals which developed NICUs had a higher percentage of their population with high risk characteristics. In spite of this, they had lower neonatal mortality rates in two categories: (1) white 3.5-5.5 pounds birthweight infants, (2) low birthweight infants whose mothers received no prenatal care. Black 3.5-5.5 pounds birthweight infants did equally well in either hospital group. While the differences between the two hospital groups for these categories were not statistically significant at the p < 0.05 level, data from the 1958-1960 period substantiate that a marked change occurred in the 3.5-5.5 pounds birthweight category for those infants born in hospitals which developed NICUs. Early data were not available for prenatal care. These findings support the conclusion that, in Houston, NICUs had some impact on neonatal mortality among moderately underweight infants. ^

The Relationship of Provincial Economic Level and Child Injury Mortality in Thailand: A Cross-Sectional Analysis in a Middle Income Country

The objective of this cross-sectional study was to examine the relationship of provincial economic development indices with incidences of child injury mortality in Thailand from 1999 - 2001. All injury deaths among children age 1-14 years were included. The independent variables included gross provincial product per capita (GPP/c), poverty and inequality indices, material and social deprivation indices, population in rural/ urban areas, and migration. Due to multicollinearity of such variables, the 76 provinces were categorized by GPP/c quartile, and means of overall injury, drowning, and transport-related mortality rates were compared among quartile groups. Spearman’s rho correlation between GPP/c and injury mortality rates was also performed. Finally, factor analysis was employed to create a set of factors to be treated as uncorrelated variables and stepwise multiple regression was carried out for the effects of the factors on injury mortality rates. A significant direct relationship was observed between GPP/c and overall injury mortality among children age 1-4 years, and 10-14 year-olds of both genders. Drowning was the main cause of this relationship among children age 1-4 years, and transport-related injury was the principle cause among children age 10-14 years. Conversely, provinces with lower GPP/c experienced higher injury mortality rates among school-age children 5-9 years old for both genders, mostly due to drowning. Factor analysis, and multiple regression results confirmed the relationships between economic development and injury mortality rates. These findings revealed that economic development had an adverse impact on injury-related mortality among children 1 to 4 and 10 to14 in Thailand.