Congential syphilis in Harris County, Texas, 1993--1996

The specific aims of this study were to: (1) To determine the incidence of congenital syphilis (CS) for the 1993-96 birth cohorts in Houston/Harris County, based on the newly revised 1989 CS surveillance definition in Houston/Harris County, Texas; (2) To study the distribution of selected variables listed in the Centers for Disease Control and Prevention (CDC) Congenital Syphilis Case Investigation and Report Form for the reported cases of CS; (3) To ascertain the relationships of maternal demographic factors, geographic distribution, and provision and utilization of prenatal care, associated with reported congenital syphilis delivery.^ This was a descriptive study analyzing reported cases of congenital syphilis in Houston/Harris, County, TX during the years 1993-96 using the data recorded on the CDC's Congenital Syphilis Case Investigation and Report forms. The population included infants delivered during 1993-96 who were diagnosed with congenital syphilis, using the revised 1990 criteria of the CDC. This study examined the risk factors associated with the occurrence of congenital syphilis in Harris County where the prevalence of maternal syphilis infection (13.7/100,000/1995) is high. (Abstract shortened by UMI.) ^

A comparison of Markov and generalized linear models of hospital mortality

This paper reports a comparison of three modeling strategies for the analysis of hospital mortality in a sample of general medicine inpatients in a Department of Veterans Affairs medical center. Logistic regression, a Markov chain model, and longitudinal logistic regression were evaluated on predictive performance as measured by the c-index and on accuracy of expected numbers of deaths compared to observed. The logistic regression used patient information collected at admission; the Markov model was comprised of two absorbing states for discharge and death and three transient states reflecting increasing severity of illness as measured by laboratory data collected during the hospital stay; longitudinal regression employed Generalized Estimating Equations (GEE) to model covariance structure for the repeated binary outcome. Results showed that the logistic regression predicted hospital mortality as well as the alternative methods but was limited in scope of application. The Markov chain provides insights into how day to day changes of illness severity lead to discharge or death. The longitudinal logistic regression showed that increasing illness trajectory is associated with hospital mortality. The conclusion is reached that for standard applications in modeling hospital mortality, logistic regression is adequate, but for new challenges facing health services research today, alternative methods are equally predictive, practical, and can provide new insights. ^

The effects of population density on the spread of disease

The objective of this study is to identify the relationship between population density and the initial stages of the spread of disease in a local population. This study proposes to concentrate on the question of how population density affects the distribution of the susceptible individuals in a local population and thus affects the spread of the disease, measles. Population density is measured by the average of the number of contacts with susceptible individuals by each individual in the population during a fixed-length time period. The term “contact with susceptible individuals” means sufficient contact between two people for the disease to pass from an infectious person to a susceptible person. The fixed-length time period is taken to be the average length of time an infected person is infectious without symptoms of the disease. For this study of measles, the time period will be seven days. ^ While much attention has been given to modeling the entire epidemic process of measles, attempts have not been made to study the characteristics of contact rates required to initiate an epidemic. This study explores the relationship between population density, given a specific herd immunity rate in the population, and initial rate of the spread of the disease by considering the underlying distribution of contacts with susceptibles by the individuals in the population. ^ This study does not seek to model an entire measles epidemic, but to model the above stated relationship for the local population within which the first infective person is introduced. This study describes the mathematical relationship between population density parameters and contact distribution parameters. ^ The results are displayed in graphs that show the effects of different population densities on the spread of disease. The results support the idea that the number of new infectives is strongly related to the distribution of susceptible contacts. The results also show large differences in the epidemic measures between populations with densities equal to four versus three. ^

Design and implementation of a multicriteria medical decision support system for diagnosis and treatment

Health care providers face the problem of trying to make decisions with inadequate information and also with an overload of (often contradictory) information. Physicians often choose treatment long before they know which disease is present. Indeed, uncertainty is intrinsic to the practice of medicine. Decision analysis can help physicians structure and work through a medical decision problem, and can provide reassurance that decisions are rational and consistent with the beliefs and preferences of other physicians and patients. ^ The primary purpose of this research project is to develop the theory, methods, techniques and tools necessary for designing and implementing a system to support solving medical decision problems. A case study involving “abdominal pain” serves as a prototype for implementing the system. The research, however, focuses on a generic class of problems and aims at covering theoretical as well as practical aspects of the system developed. ^ The main contributions of this research are: (1) bridging the gap between the statistical approach and the knowledge-based (expert) approach to medical decision making; (2) linking a collection of methods, techniques and tools together to allow for the design of a medical decision support system, based on a framework that involves the Analytic Network Process (ANP), the generalization of the Analytic Hierarchy Process (AHP) to dependence and feedback, for problems involving diagnosis and treatment; (3) enhancing the representation and manipulation of uncertainty in the ANP framework by incorporating group consensus weights; and (4) developing a computer program to assist in the implementation of the system. ^

Risk, outcomes, and cost of emergency center visits in cancer patients

Cancer is a chronic disease that often necessitates recurrent hospitalizations, a costly pattern of medical care utilization. In chronically ill patients, most readmissions are for treatment of the same condition that caused the preceding hospitalization. There is concern that rather than reducing costs, earlier discharge may shift costs from the initial hospitalization to emergency center visits. ^ This is the first descriptive study to measure the incidence of emergency center visits (ECVs) after hospitalization at The University of M. D. Anderson Cancer Center (UTMDACC), to identify the risk factors for and outcomes of these ECVs, and to compare 30-day all-cause mortality and costs for episodes of care with and without ECVs. ^ We identified all hospitalizations at UTMDACC with admission dates from September 1, 1993 through August 31, 1997 which met inclusion criteria. Data were electronically obtained primarily from UTMDACC's institutional database. Demographic factors, clinical factors, duration of the index hospitalization, method of payment for care, and year of hospitalization study were variables determined for each hospitalization. ^ The overall incidence of ECVs was 18%. Forty-five percent of ECVs resulted in hospital readmission (8% of all hospitalizations). In 1% of ECVs the patient died in the emergency center, and for the remaining 54% of ECVs the patient was discharged home. Risk factors for ECVs were marital status, type of index hospitalization, cancer type, and duration of the index hospitalization. The overall 30-day all-cause mortality rate was 8.6% for hospitalizations with an ECV and 5.3% for those without an ECV. In all subgroups, the 30-day all-cause mortality rate was higher for groups with ECVs than for those without ECVs. The most important factor increasing cost was having an ECV. In all patient subgroups, the cost per episode of care with an ECV was at least 1.9 times the cost per episode without an ECV. ^ The higher costs and poorer outcomes of episodes of care with ECVs and hospital readmissions suggest that interventions to avoid these ECVs or mitigate their costs are needed. Further research is needed to improve understanding of the methodological issues involved in relation to health care issues for cancer patients. ^

Sequential updating via dynamic hierarchical models: A Bayesian approach to longitudinal data analysis

Most statistical analysis, theory and practice, is concerned with static models; models with a proposed set of parameters whose values are fixed across observational units. Static models implicitly assume that the quantified relationships remain the same across the design space of the data. While this is reasonable under many circumstances this can be a dangerous assumption when dealing with sequentially ordered data. The mere passage of time always brings fresh considerations and the interrelationships among parameters, or subsets of parameters, may need to be continually revised. ^ When data are gathered sequentially dynamic interim monitoring may be useful as new subject-specific parameters are introduced with each new observational unit. Sequential imputation via dynamic hierarchical models is an efficient strategy for handling missing data and analyzing longitudinal studies. Dynamic conditional independence models offers a flexible framework that exploits the Bayesian updating scheme for capturing the evolution of both the population and individual effects over time. While static models often describe aggregate information well they often do not reflect conflicts in the information at the individual level. Dynamic models prove advantageous over static models in capturing both individual and aggregate trends. Computations for such models can be carried out via the Gibbs sampler. An application using a small sample repeated measures normally distributed growth curve data is presented. ^

Detection of enterotoxigenic Escherichia coli in foods by polymerase chain reaction

Enterotoxigenic Escherichia coli (ETEC) causes significant morbidity and mortality in infants of developing countries and is the most common cause of diarrhea in travelers to these areas. Enterotoxigenic Escherichia coli infections are commonly caused by ingestion of fecally contaminated food. A timely method for the detection of ETEC in foods would be important in the prevention of this disease. A multiplex polymerase chain reaction (PCR) assay which has been successful in detecting the heat-labile and heat-stable toxins of ETEC in stool was examined to determine its utility in foods. This PCR assay, preceded by a glass matrix and chaotropic DNA extraction, was effective in detecting high numbers of ETEC in a variety of foods. Ninety percent of 121 spiked food samples yielded positive results. Samples of salsa from Guadalajara, Mexico and Houston, Texas were collected and underwent DNA extraction and PCR. All samples yielded negative results for both the heat-labile and heat-stable toxins. Samples were also subjected to oligonucleotide probe analysis and resulted in 5 samples positive for ETEC. Upon dilution testing, it was found that positive PCR results only occurred when 12,000 to 1,000,000 bacteria were present in 200 mg of food. Although the DNA extraction and PCR method has been shown to be both sensitive and specific in stool, similar results were not obtained in food samples. ^

Prediction of cardiovascular disease risk factors in Mexican-American children from parental risk factors, and social and demographic characteristics in the HHANES

Objectives. Cardiovascular disease (CVD) including CVD secondary to diabetes type II, a significant health problem among Mexican American populations, originates in early childhood. This study seeks to determine risk factors available to the health practitioner that can identify the child at potential risk of developing CVD, thereby enabling early intervention. ^ Design. This is a secondary analysis of cross-sectional data of matched Mexican American parents and children selected from the HHANES, 1982–1984. ^ Methods. Parents at high risk for CVD were identified based on medical history, and clinical and physical findings. Factor analysis was performed on children's skinfold thicknesses, height, weight, and systolic and diastolic blood pressures, in order to produce a limited number of uncorrelated child CVD risk factors. Multiple regression analyses were then performed to determine other CVD markers associated with these Factors, independently for mothers and fathers. ^ Results. Factor analysis of children's measurements revealed three uncorrelated latent variables summarizing the children's CVD risk: Factor1: ‘Fatness’, Factor2: ‘Size and Maturity’, and Factor3: ‘Blood Pressure’, together accounting for the bulk of variation in children's measurements (86–89%). Univariate analyses showed that children from high CVD risk families did not differ from children of low risk families in occurrence of high blood pressure, overweight, biological maturity, acculturation score, or social and economic indicators. However, multiple regression using the factor scores (from factor analysis) as dependent variables, revealed that higher CVD risk in parents, was significantly associated with increased fatness and increased blood pressure in the children. Father's CVD risk status was associated with higher levels of body fat in his children and higher levels of blood pressure in sons. Mother's CVD risk status was associated with higher blood pressure levels in children, and occurrence of obesity in the mother associated with higher fatness levels in her children. ^ Conclusion. Occurrence of cardiovascular disease and its risk factors in parents of Mexican American children, may be used to identify children at potentially higher risk for developing CV disease in the future. Obesity in mothers appears to be an important marker for the development of higher levels of body fatness in children. ^

Behavioral and psychosocial factors associated with sexual risk in a population of crack cocaine users

The purpose of this dissertation was to examine the relationship between key psychosocial and behavioral components of the Transtheoretical Model and the Theory of Reasoned Action for sexual risk reduction in a population of crack cocaine smokers and sex workers, not in drug treatment. ^ The first study examined the results of an analysis of the association between two principal constructs in the Transtheoretical Model, the processes of change and the stages of change for condom use, in a high risk population. In the analysis of variance for all respondents, the overall F-test revealed that people in different stages have different levels of experiential process use, F(3,317) = 17.79, p = 0.0001 and different levels of behavioral process use, F(3,317) = 28.59, p = .0001. For the experiential processes, there was a significant difference between the precontemplation/contemplation stage, and both the action, and maintenance, stages.^ The second study explored the relationship between the Theory of Reasoned Action “beliefs” and the stages-of-change in the same population. In the analysis of variance for all participants, the results indicate that people in different stages did value the positive beliefs differently, F(3,502) = 15.38, p = .0001 but did not value the negative beliefs differently, F(3,502) = 2.08, p = .10. ^ The third study explored differences in stage-of-change by gender, partner type drug use, and HIV status. Three discriminant functions emerged, with a combined χ2(12) = 139.57, p = <.0001. The loading matrix of correlations between predictors and discriminant functions demonstrate that the strongest predictor for distinguishing between the precontemplation/contemplation stage and the preparation, action, and maintenance stages (first function) is partner type (.962). The loadings on the second discriminant function suggest that once partner type has been accounted for, ever having HIV/AIDS (.935) was the best predictor for distinguishing between the first three stages and the maintenance stage. ^ These studies demonstrate that behavioral change theories can contribute important insight to researchers and program planners attempting to alter HIV risk behavior in high-risk populations. ^

Effect of cancer chemotherapy on the frequency of minisatellite repeat number changes in human sperm

The objective of this study was to determine whether cancer chemotherapy induces detectable mutations in DNA of the human germline and whether minisatellite repeat number changes can be used as a sensitive indicator of genetic damage in human sperm caused by mutagens. We compared the mutation frequencies in sperm of the same cancer patients pre- and post-, pre- and during, or during and post-treatment. Small pool polymerase chain reaction (SP-PCR) (DNA equivalent to approximately 100 sperm) and Southern blotting techniques were used to detect mutations and quantify the frequency of repeat number changes at the minisatellite MS205 locus. One pre- and one post-treatment semen sample was obtained from each Hodgkin's disease patient treated with either: (1) a regimen without alkylating agents, Novantrone, Oncovin, Vinblastine, and Prednisone (NOVP), 4 patients; (2) a regimen containing alkylating agents, Cytoxan, Vinblastine, Procarbazine, and Prednisone (CVPP)/Adriamycin, Bleomycin, DTIC, CCNU, and Prednisone (ABDIC), 2 patients; and (3) a regimen containing alkylating agents, Mechlorethamine, Oncovin, Procarbazine, and Prednisone (MOPP), 1 patient. One pre- and one during treatment semen sample from each of two Hodgkin's disease patients treated with Adriamycin, Bleomycin, Vinblastine, and Dacarbazine (ABVD) were obtained. One during and one post-treatment semen sample from a Hodgkin's disease patient treated with NOVP were also obtained. At least 7900 sperm in each sample were screened for the repeat number changes at the MS205 locus by multi-aliquots of SP-PCR. The mutation frequencies of pre- and post-treatment for the four patients treated with NOVP were 0.22 and 0.18%; 0.24 and 0.16%; 0.35 and 0.28%; and 0.19 and 0.18%. With CVPP/ABDIC, they were 0.22 and 0.23%; and 0.94 and 0.98% for the two patients and with MOPP they were 0.79 and 1.14%. The mutation frequencies of pre- and during treatment with ABVD were 0.09 and 0.07%; and 0.34 and 0.27% for the two patients. The mutation frequencies of during and post-treatment with NOVP for one patient were 0.31 and 0.25%. A statistically significant increase in mutation frequency was only found in the patient treated with MOPP. According to the time of samples collected after or during treatment and the above results, we conclude that there is no effect of NOVP and CVPP/ABDIC regimens on the mutation frequency in spermatogonia. The spermatocytes are not highly sensitive to chemotherapy agents compared to spermatogonia at the minisatellite MS205 locus. MOPP treatment may increase the mutation frequency at the MS205 locus in spermatogonia. ^

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 location of majority and minority populations with respect to commercial treatment, storage, and disposal facilities in Texas

There is a growing interest in the location of Treatment, Storage, and Disposal (TSDF) sites in relation to minority communities. A number of studies have been completed, and the results of these studies have been varied. Some of the studies have shown a strong positive correlation between the location of TSDF sites and minority populations, while a few have shown no significance in that relationship. The major difference between these studies has been in the areal unit used.^ This study compared the minority populations of Texas census tracts and ZIP codes containing a TSDF using the associated county as the comparison population. The hypothesis of this study was that there was no difference between using census tracts and ZIP codes to analyze the relationship of minority populations and TSDF's. The census data used was from 1990, and the initial list of TSDF sites was supplied by the Texas Natural Resource Conservation Commission. The TSDF site locations were checked using graphical information systems (GIS) programs, in order to increase the accuracy of the identity of exposed ZIP codes and census tracts. The minority populations of the exposed areal units were compared using proportional differences, crosstables, maps, and logistic regression. The dependent variable used was the exposure status of the areal units under study, including counties, census tracts, and ZIP codes. The independent variables used included minority group proportion and grouping of the proportions, educational status, household income, and home value.^ In all cases, education was significant or near significant at the.05 level. Education rather than minority proportion was therefore the most significant predictor of the exposure status of a census tract or ZIP code. ^

Relationship between enterotoxigenic Escherichia coli and travelers' diarrhea in Mexico, from 1992 to 1997

The purpose of this study was to examine the relationship between enterotoxigenic ETEC and travelers' diarrhea over a period of five years in Guadalajara, Mexico. Specifically, this study identified and characterized ETEC from travelers with diarrhea. The objectives were to study the colonization factor antigens, toxins and antibiotic sensitivity patterns in ETEC from 1992 to 1997 and to study the molecular epidemiology of ETEC by plasmid content and DNA restriction fragment patterns. ^ In this survey of travelers' diarrhea in Guadalajara, Mexico, 928 travelers with diarrhea were screened for enteric pathogens between 1992 and 1997. ETEC were isolated in 195 (19.9%) of the patients, representing the most frequent enteric pathogen identified. ^ A total of 31 antimicrobial susceptibility patterns were identified among ETEC isolates over the five-year period. ^ The 195 ETEC isolates contained two to six plasmids each, which ranged in size from 2.0 to 23 kbp. ^ Three different reproducible rRNA gene restriction patterns (ribotypes R-1 to R-3) were obtained among the 195 isolates with the enzyme, HindIII. ^ Colonization factor antigens (CFAs) were identified in 99 (51%) of the 195 ETEC strains studied. ^ Cluster analysis of the observations seen in the four assays all confirmed the five distinct groups of study-year strains of ETEC. Each group had a >95% similarity level of strains within the group and <60% similarity level between the groups. In addition, discriminant analysis of assay variables used in predicting the ETEC strains, reveal a >80% relationship between both the plasmid and rRNA content of ETEC strains and study-year. ^ These findings, based on laboratory observations of the differences in biochemical, antimicrobial susceptibility, plasmid and ribotype content, suggest complex epidemiology for ETEC strains in a population with travelers' diarrhea. The findings of this study may have implications for our understanding of the epidemiology, transmission, treatment, control and prevention of the disease. It has been suggested that an ETEC vaccine for humans should contain the most prevalent CFAs. Therefore, it is important to know the prevalence of these factors in ETEC in various geographical areas. ^ CFAs described in this dissertation may be used in different epidemiological studies in which the prevalence of CFAs and other properties on ETEC will be evaluated. Furthermore, in spite of an intense search in near 200 ETEC isolates for strains that may have clonal relationship, we failed to identify such strains. However, further studies are in progress to construct suitable live vaccine strains and to introduce several of CFAs in the same host organism by recombinant DNA techniques (Dr. Ann-Mari Svennerholm's lab). (Abstract shortened by UMI.)^

Cultural beliefs and hypertension in rural Philippines

Hypertension (HTN), the major risk factor for cardiovascular disease (CVD), is emerging as a major public health problem in the Philippines. CVD has been the leading cause of mortality in the Philippines since 1990. ^ Although research has shown that certain populations have a greater propensity for HTN, and that culture may be a factor, empirical investigations of the influence of cultural beliefs on HTN are lacking. ^ The operational aims of this study were to: (a) develop and examine the reliability (test-retest, internal consistency) and validity (content) of a questionnaire which measures factors related to HTN; (b) administer the questionnaire; and (c) measure blood pressure, height, and weight of the ≥ 30 year old residents of San Antonio, Nueva Ecija, Philippines. ^ The analytic aims were to determine the: (a) cultural beliefs relating to HTN; (b) associations between cultural beliefs and HTN; and (c) extent to which cultural beliefs versus biological, behavioral, socioeconomic, and access factors are associated with HTN. ^ A cluster survey was conducted among 336 residents ≥ 30 years old in May, 1998. Sixty clusters of households were derived using probability proportionate to size sampling technique. Seven households per cluster were visited and one respondent per household was randomly chosen for interview and measurement of blood pressure, height and weight. A response rate of 84% (336/400) was achieved. ^ Results showed that the test-retest reliability of cultural belief items was 0.69–0.96. Internal consistency reliability was 0.74. ^ HTN (SBP ≥ 140; or DBP ≥ 90 mmHg; or currently taking anti-hypertensive medication) prevalence was 23/100. Univariate logistic regression showed cultural beliefs to be significantly associated (p < 0.037) with HTN. However, multivariate analysis showed that only age ≥ 50 (p = 0.000), family history of HTN (p = 0.004) and body mass index ≥ 25 (p = 0.003) were significant predictors. ^ In the absence of fully implemented programs to prevent and control HTN, the current prevalence is only expected to increase, leading to substantial increases in morbidity and mortality and health care cost. It is recommended that research which focuses on designing, implementing, and evaluating culturally appropriate community-wide programs on HTN prevention and control be undertaken in this community. ^

Exposure to the Asp f 1 allergen in nonindustrial occupational environments

Sick Building Syndrome is a prevalent problem with patient complaints similar to typical allergy symptoms. Unlike most household allergens, the Asp f 1 allergen is conceivably ubiquitous in the work environment. This project examined levels of the Asp f 1 allergen in office and non-industrial occupational environments, and studied the bioaerosol and dust reservoirs of Aspergillus fumigatus responsible for those levels. ^ Culturable bioaerosols of total mesophilic fungi were sampled with Andersen N6 impactors. Aggressive airborne and bulk dust samples were concurrently collected and assayed for Asp f 1. Bulk dusts were selectively cultured for A. fumigatus. Samples were collected during both wet and dry climatological conditions to examine the possibility of Asp f 1 increases due to fungal growth blooms. ^ Only very low levels of Asp f 1 were detected in relatively few samples. Analysis of wet versus dry period samples showed no differences in Asp f 1 levels, although A. fumigatus counts from dusts did fluctuate significantly with exterior moisture events as did indoor prevalence of total colony forming units. These results indicate that even in the presence of elevated fungal concentrations, levels of Asp f 1 are extremely low. These levels do not correlate with climatological moisture events, despite distinct fungal blooms in the days immediately following those events. Non-industrial office buildings devoid of indoor air quality issues did not demonstrate significant levels or occurrence of Asp f 1 contamination in the geographical region of this study. ^