Public Health Commons^™

An Empirical Study Of Marginal Structural Models For Time-Independent Treatment, Tanya A. Henneman, Mark J. Van Der Laan

U.C. Berkeley Division of Biostatistics Working Paper Series

In non-randomized treatment studies a significant problem for statisticians is determining how best to adjust for confounders. Marginal structural models (MSMs) and inverse probability of treatment weighted (IPTW) estimators are useful in analyzing the causal effect of treatment in observational studies. Given an IPTW estimator a doubly robust augmented IPTW (AIPTW) estimator orthogonalizes it resulting in a more e±cient estimator than the IPTW estimator. One purpose of this paper is to make a practical comparison between the IPTW estimator and the doubly robust AIPTW estimator via a series of Monte- Carlo simulations. We also consider the selection of the optimal …

The Analysis Of Placement Values For Evaluating Discriminatory Measures, Margaret S. Pepe, Tianxi Cai

UW Biostatistics Working Paper Series

The idea of using measurements such as biomarkers, clinical data, or molecular biology assays for classification and prediction is popular in modern medicine. The scientific evaluation of such measures includes assessing the accuracy with which they predict the outcome of interest. Receiver operating characteristic curves are commonly used for evaluating the accuracy of diagnostic tests. They can be applied more broadly, indeed to any problem involving classification to two states or populations (D = 0 or D = 1). We show that the ROC curve can be interpreted as a cumulative distribution function for the discriminatory measure Y in the …

Case-Control Current Status Data, Nicholas P. Jewell, Mark J. Van Der Laan

U.C. Berkeley Division of Biostatistics Working Paper Series

Current status observation on survival times has recently been widely studied. An extreme form of interval censoring, this data structure refers to situations where the only available information on a survival random variable, T, is whether or not T exceeds a random independent monitoring time C, a binary random variable, Y. To date, nonparametric analyses of current status data have assumed the availability of i.i.d. random samples of the random variable (Y, C), or a similar random sample at each of a set of fixed monitoring times. In many situations, it is useful to consider a case-control sampling scheme. Here, …

Current Status Data: Review, Recent Developments And Open Problems, Nicholas P. Jewell, Mark J. Van Der Laan

U.C. Berkeley Division of Biostatistics Working Paper Series

Researchers working with survival data are by now adept at handling issues associated with incomplete data, particular those associated with various forms of censoring. An extreme form of interval censoring, known as current status observation, refers to situations where the only available information on a survival random variable T is whether or not T exceeds a random independent monitoring time C. This article contains a brief review of the extensive literature on the analysis of current status data, discussing the implications of response-based sampling on these methods. The majority of the paper introduces some recent extensions of these ideas to …

Production Of A Monoclonal Antibody Against Benzo[Α]Pyrene Diol Epoxide Dna Adducts, Brian Peden Austin

Chemistry & Biochemistry Theses & Dissertations

Benzo[α]pyrene is a ubiquitous pollutant produced from the incomplete combustion of organic material such as fossil fuels. It is found in the workplace, urban air, drinking water, and the food supply. Recently, it has been proposed that benzo[α]pyrene may be the causative agent in the formation of lung adenocarcinomas among some Taiwanese women exposed to cooking oil fumes without adequate ventilation. In this study, calf thymus DNA was modified in vitro with benzo[α]pyrene-diol epoxide (BPDE) to a level consistent with that found in biological samples. This DNA of low modification was used as an immunogen in the production of a …

Bse: Risk, Uncertainty, And Policy Change, Enda Cummins, Pat Grace, Kevin Mcdonnell, Shane Ward

RISK: Health, Safety & Environment (1990-2002)

The authors discuss how, in our "risk society," a range of potential risks and uncertainties are associated with new technologies and new diseases, such as BSE. These risks bring with them worries about human health, while the ability to assess and manage new health scares is an essential skill for government and related industries.

Estimating Causal Parameters In Marginal Structural Models With Unmeasured Confounders Using Instrumental Variables, Tanya A. Henneman, Mark Johannes Van Der Laan, Alan E. Hubbard

U.C. Berkeley Division of Biostatistics Working Paper Series

For statisticians analyzing medical data, a significant problem in determining the causal effect of a treatment on a particular outcome of interest, is how to control for unmeasured confounders. Techniques using instrumental variables (IV) have been developed to estimate causal parameters in the presence of unmeasured confounders. In this paper we apply IV methods to both linear and non-linear marginal structural models. We study a specific class of generalized estimating equations that is appropriate to these data, and compare the performance of the resulting estimator to the standard IV method, a two-stage least squares procedure. Our results are applied to …

Surveillance For Waterborne-Disease Outbreaks--United States, 1999-2000, Sherline H. Lee, Deborah A. Levy, Gunther F. Craun, Michael J. Beach, Rebecca L. Calderon

Journal Articles: Epidemiology

PROBLEM/CONDITION: Since 1971, CDC, the U.S. Environmental Protection Agency (EPA), and the Council of State and Territorial Epidemiologists (CSTE) have maintained a collaborative surveillance system for the occurrences and causes of waterborne-disease outbreaks (WBDOs).This surveillance system is the primary source of data concerning the scope and effects of waterborne diseases on persons in the United States.

REPORTING PERIOD COVERED: This summary includes data regarding outbreaks occurring during January 1999-December 2000 and previously unreported outbreaks occurring in 1995 and 1997.

DESCRIPTION OF THE SYSTEM: The surveillance system includes data for outbreaks associated with drinking water and recreational water. State, territorial, and …

Associations Between Water-Treatment Methods And Diarrhoea In Hiv-Positive Individuals, J. N. S. Eisenberg, T. J. Wade, A. Hubbard, D. I. Abrams, R. J. Leiser, S. Charles, M. Vu, S. Saha, C. C. Wright, Deborah A. Levy, P. Jensen, J. M. Colford

Journal Articles: Epidemiology

This manuscript extends our previously published work (based on data from one clinic) on the association between three drinking water-treatment modalities (boiling, filtering, and bottling) and diarrhoeal disease in HIV-positive persons by incorporating data from two additional clinics collected in the following year. We conducted a cross-sectional survey of drinking water patterns, medication usage, and episodes of diarrhoea among HIV-positive persons attending clinics associated with the San Francisco Community Consortium. We present combined results from our previously published work in one clinic (n = 226) with data from these two additional clinics (n = 458). In this combined analysis we …

Risk Factors In Hiv-Associated Diarrhoeal Disease: The Role Of Drinking Water, Medication And Immune Status, J. N. S. Eisenberg, T. J. Wade, S. Charles, M. Vu, A. Hubbard, C. C. Wright, Deborah A. Levy, P. Jensen, J. M. Colford

Journal Articles: Epidemiology

In a cross-sectional survey of 226 HIV-infected men, we examined the occurrence of diarrhoea and its relationship to drinking water consumption patterns, risk behaviours, immune status and medication use. Diarrhoea was reported by 47% of the respondents. Neither drinking boiled nor filtered water was significantly associated with diarrhoea (OR = 0.5 [0.2, 1.6], 1.2 [0.6, 2.5] respectively), whereas those that drank bottled water were at risk for diarrhoea (OR = 3.0 [1.1, 7.8]). Overall, 47% always or often used at least one water treatment. Of the 37% who were very concerned about drinking water, 62% had diarrhoea, 70% always or …

Participant Blinding And Gastrointestinal Illness In A Randomized, Controlled Trial Of An In-Home Drinking Water Intervention, John M. Colford, Judy R. Rees, Timothy J. Wade, Asheena Khalakdina, Joan F. Hilton, Isaac J. Ergas, Susan Burns, Anne Benker, Catherine Ma, Cliff Bowen, Daniel C. Mills, Duc J. Vugia, Dennis D. Juranek, Deborah A. Levy

Journal Articles: Epidemiology

We conducted a randomized, triple-blinded home drinking water intervention trial to determine if a large study could be undertaken while successfully blinding participants. Households were randomized 50:50 to use externally identical active or sham treatment devices. We measured the effectiveness of blinding of participants by using a published blinding index in which values >0.5 indicate successful blinding. The principal health outcome measured was "highly credible gastrointestinal illness" (HCGI). Participants (n=236) from 77 households were successfully blinded to their treatment assignment. At the end of the study, the blinding index was 0.64 (95% confidence interval 0.51-0.78). There were 103 episodes of …

The Role Of Diet And Physical Activity For Ovarian Cancer Results From The Adventist Health Study, Fatemeh Kiani

Loma Linda University Electronic Theses, Dissertations & Projects

A few aspects of the epidemiology of ovarian cancer are well understood, such as the inverse relationship with parity and oral contraceptive (OC) use. The role of other factors such as the potential influence of diet or physical activity is far from being established. A few studies, however, have been able to identify dietary risk factors for ovarian cancer. In this dissertation, I have conducted two studies that investigate the relationship between dietary factors and physical activity and the three endpoints: 1) nonfatal ovarian cancer (1976-1982; time to diagnosis), 2) fatal ovarian cancer (1976-1988; time to death), and 3) total …

Evaluation Of Directly Observed Therapy In Pulmonary Tuberculosis Patients In Nepal: Treatment Outcome And Patient Compliance, Baishali Bhattacharya

Masters Theses & Specialist Projects

Tuberculosis is the leading cause of infectious disease in Nepal. An estimated 60% of the adult population aged between 15-45 years is infected with tuberculosis, and 45% of the total population is infected. Ten percent of people infected with TB progress to active disease. To combat tuberculosis, Directly Observed Therapy (DOT) was adopted in Nepal in 1996. DOT was administered at four national demonstration sites in 1996 and expanded over time so that 56% of the population to date have been covered by DOT. This study aimed to evaluate DOT in pulmonary TB patients in Nepal in terms of patient …

Acquired Immuno-Deficiency Syndrome (Aids) And Human Immuno-Deficiency Virus (Hiv) In Nevada – Annual Surveillance Report (1999), Mary Guinan, Nancy Kreher, Drew Mather, Wei Yang

School of Public Health Faculty Research

Background:

Acquired Immuno-Deficiency Syndrome (AIDS) is the most severe manifestation of Human Immunodeficiency Virus (HIV) infection. AIDS was first reported in the world in 1981 by the Centers for Disease Control and Prevention. Statewide surveillance for AIDS was begun in 1982. Because the cause of AIDS was unknown at that time, the surveillance case definition included many opportunistic infections and tumors. Persons with AIDS were noted to have abnormalities in their immune system that left them susceptible to certain infections. As more information became available, the AIDS surveillance case definition was modified.

In 1984, HIV was found to be the …

A Model For Hiv/Aids Risk Behaviors Of Students In Armenia, Talin Babikian

Loma Linda University Electronic Theses, Dissertations & Projects

Without a cure in now its third decade, AIDS is a concern for both the medical and social science disciplines. Most at risk for a nationwide AIDS epidemic are developing countries, which often lack the necessary resources and knowledge to minimize the spread of the disease. There are an estimated 1500 HIV cases in Armenia, 81.5% of which occur in the 20-39 age group. Armenia’s current economic and political instability, increase in sexually transmitted infections (STI), prostitution, and injecting drug use, and the alarming incidence rates in neighboring countries amplify its risk for a national epidemic.

The goals of this …

Tractor Driving Among Kentucky Farm Youth: Results From The Farm Family Health And Hazard Surveillance Project, Steven R. Browning, Susan C. Westneat, Raeanne Szeluga

Epidemiology and Environmental Health Faculty Publications

This article documents the extent of children's involvement in tractor operations among a representative sample of Kentucky children living and working on family farms. Specifically, we describe children's exposures to tractor-related work activities, profile their use of the tractor (number of days worked), and assess compliance with generally recommended safety measures, such as using tractors equipped with ROPS (rollover protective structures), avoiding riding as passengers on tractors, and operating tractors on public roadways. Data for this study were collected in 1994 and 1995 as part of the NIOSH-sponsored Farm Family Health and Hazard Surveillance Project (FFHHSP). Despite recognition in the …

The Mind-Body Problem: A Tuberculosis/Tobacco Example, Ibpp Editor

International Bulletin of Political Psychology

This article illustrates two conflicts between what is, perhaps, best for the mind and best for the body.

How Peruvian Mothers Appraise Pneumonia And The Predictors Of Their Intention To Seek Medical Care When Their Children Have Signs Of Pneumonia, César Augusto Gálvez

Loma Linda University Electronic Theses, Dissertations & Projects

Pneumonia ranks first in health problems demanding attention, and second in the cause of mortality for children under five years old in Peru (Toledo, & Minaya, 1999). Studies about behavioral determinants that influence mothers to seek medical help for their child with signs of pneumonia do not focus on the contribution of the behavioral determinants to intention of seeking medical help.

Using the Theory of Planned Behavior (TPB) and a cross-sectional design, the objectives of this study were to know first, Peruvian mothers' perceptions about knowledge and recognition of pneumonia, and about the government pneumonia campaign (GPC). Second, mothers' attitudes, …

European Madness And Mad Cow Disease, Ibpp Editor

International Bulletin of Political Psychology

This article describes some of the psychological factors that might attenuate unadaptive anxieties about the threat of bovine spongiform encephalopathy, mad cow disease.

Trends. Biopolitics And Anthrax: A United States Fiasco?, Ibpp Editor

International Bulletin of Political Psychology

This article discusses the biopolitical issues involved with the mass inoculation of United States military forces against anthrax.

Chronic Arsenic Exposure And Risk Of Infant Mortality In Two Areas Of Chile, Claudia Hopenhayn-Rich, Steven R. Browning, Irva Hertz-Picciotto, Catterina Ferreccio, Cecilia Peralta, Herman Gibb

Preventive Medicine and Environmental Health Faculty Publications

Chronic arsenic exposure has been associated with a range of neurologic, vascular, dermatologic, and carcinogenic effects. However, limited research has been directed at the association of arsenic exposure and human reproductive health outcomes. The principal aim of this study was to investigate the trends in infant mortality between two geographic locations in Chile: Antofagasta, which has a well-documented history of arsenic exposure from naturally contaminated water, and Valparaíso, a comparable low-exposure city. The arsenic concentration in Antofagasta's public drinking water supply rose substantially in 1958 with the introduction of a new water source, and remained elevated until 1970. We used …

Chemopreventive Effect Of Oltipraz On Afb1-Induced Hepatocarcinogenesis In Tree Shrew Model, Yuan Li, Jian Jia Su, Liu L. Qin, Chun Yang, Dan Luo, Ke C. Ban, T. W. Kensler, B. D. Roebuck

Dartmouth Scholarship

Hepatocellular carcinoma (HCC) is one of the major cancers in the world with a mortality of more than 250 000 cases yearly. More than 137 000 cases of HCC were diagnosed each year in China, which acount approximately for more than 40 percent of the total number in the world. HCC has become the second major cause of death for cancer in China since 1990, and its annual mortality is expected to be 21.2 cases per 100 000 population in the year 2000. Even though progresses have been achieved for HCC diagnosis and treat ment, its 5-year mortality is still …

Trends. Controlling Aids Through Control, Ibpp Editor

International Bulletin of Political Psychology

This article discusses the concept of political control and public health in the context of the HIV/AIDS epidemic.

Integronlike Structures In Campylobacter Spp. Of Human And Animal Origin, Brigid Lucey, D. Crowley, P. Moloney, B. Cryan, M. Daly, F. O'Halloran, E. J. Threlfall, S. Fanning

Department of Biological Sciences Publications

Resistance to antimicrobial agents used to treat severe Campylobacter spp. gastroenteritis is increasing worldwide. We assessed the antimicrobial resistance patterns of Campylobacter spp. isolates of human and animal origin. More than half (n = 32) were resistant to sulphonamide, a feature known to be associated with the presence of integrons. Analysis of these integrons will further our understanding of Campylobacter spp. epidemiology.

Sulfa Or Sulfone Prophylaxis And Geographic Region Predict Mutations In The Pneumocystis Carinii Dihydropteroate Synthase Gene, Laurence Huang, Charles B. Beard, Jennifer Creasman, Deborah A. Levy, Jeffrey S. Duchin, Sherline Lee, Norman Pieniazek, Jane L. Carter, Carlos Del Rio, David Rimland, Thomas R. Navin

Journal Articles: Epidemiology

To determine factors associated with mutations in the Pneumocystis carinii dihydropteroate synthase (DHPS) gene, a prospective study of human immunodeficiency virus (HIV)-infected patients with confirmed P. carinii pneumonia was conducted in Atlanta, Seattle, and San Francisco. Clinical information was obtained from patient interview and chart abstraction. DHPS genotype was determined from DNA sequencing. Overall, 76 (68.5%) of 111 patients had a mutant DHPS genotype, including 22 (81.5%) of 27 patients from San Francisco. In multivariate analysis, sulfa or sulfone prophylaxis and study site were independent predictors of a mutant genotype. Fourteen (53.8%) of 26 patients who were newly diagnosed with …

Genetic Variation In Pneumocystis Carinii Isolates From Different Geographic Regions: Implications For Transmission, Charles B. Beard, Jane L. Carter, Scott P. Keely, Laurence Huang, Norman J. Pieniazek, Iaci N. S. Moura, Jacquelin M. Roberts, Allen W. Hightower, Michelle S. Bens, Amanda R. Freeman, Sherline Lee, James R. Stringer, Jeffrey S. Duchin, Carlos Del Rio, David Rimland, Robert P. Baughman, Deborah A. Levy, Vance J. Dietz, Paul Simon, Thomas R. Navin

Journal Articles: Epidemiology

To study transmission patterns of Pneumocystis carinii pneumonia (PCP) in persons with AIDS, we evaluated P. carinii isolates from patients in five U.S. cities for variation at two independent genetic loci, the mitochondrial large subunit rRNA and dihydropteroate synthase. Fourteen unique multilocus genotypes were observed in 191 isolates that were examined at both loci. Mixed infections, accounting for 17.8% of cases, were associated with primary PCP. Genotype frequency distribution patterns varied by patients' place of diagnosis but not by place of birth. Genetic variation at the two loci suggests three probable characteristics of transmission: that most cases of PCP do …

Surveillance For Waterborne-Disease Outbreaks--United States, 1997-1998., Rachel S. Barwick, Deborah A. Levy, Gunther F. Craun, Michael J. Beach, Rebecca L. Calderon

Journal Articles: Epidemiology

PROBLEM/CONDITION: Since 1971, CDC and the U.S. Environmental Protection Agency (EPA) have maintained a collaborative surveillance system for collecting and periodically reporting data relating to occurrences and causes of waterborne-disease outbreaks (WBDOs).

REPORTING PERIOD COVERED: This summary includes data from January 1997 through December 1998 and a previously unreported outbreak in 1996.

DESCRIPTION OF THE SYSTEM: The surveillance system includes data regarding outbreaks associated with drinking water and recreational water. State, territorial, and local public health departments are primarily responsible for detecting and investigating WBDOs and voluntarily reporting them to CDC on a standard form.

RESULTS: During 1997-1998, a total …

Resurgence Of Sleeping Sickness In Tambura County, Sudan, Anne Moore, Michaleen Richer, Mario Enrile, Edward Losio, Jacquelin Roberts, Deborah A. Levy

Journal Articles: Epidemiology

Endemic foci of human African trypanosomiasis are present in southern Sudan. In 1996 and 1997, trypanosomiasis increased sharply in Tambura County. To define the magnitude and geographic distribution of the outbreak, we conducted a prevalence survey using population-based cluster sampling in 16 villages: 1,358 participants answered questions about routine activities and tsetse fly contact and received serologic testing. Seroprevalence in the surveyed area was 19.4% (95% confidence interval = 16.9%, 21.8%). We confirmed infection in 66% of seropositive persons who received one parasitologic examination and in 95% of those who had serial examinations of lymph node fluid and blood. Activities …

Body Weight And Mortality Among Adults Who Never Smoked, Pramil N. Singh

Loma Linda University Electronic Theses, Dissertations & Projects

Most prospective studies identify an increased mortality risk for adults of high body mass index (> 27 kg/m²) that is commonly attributed to the effects of excess body fat, and also identify an increased mortality risk for adults of low body mass index (< 21 kg/m²), an association that, if causal among healthy adults, is without adequate pathophysiologic support.

In this dissertation, I have conducted three studies that continue the investigation of adiposity in relation to mortality among never-smoking adults of the California Seventh-day Adventist population. Among never-smoking adults of the Adventist Mortality Study (1960-1985), the relation between …

Assessing The Accuracy Of A New Diagnostic Test When A Gold Standard Does Not Exist, Todd A. Alonzo, Margaret S. Pepe

UW Biostatistics Working Paper Series

Often the accuracy of a new diagnostic test must be assessed when a perfect gold standard does not exist. Use of an imperfect test biases the accuracy estimates of the new test. This paper reviews existing approaches to this problem including discrepant resolution and latent class analysis. Deficiencies with these approaches are identified. A new approach is proposed that combines the results of several imperfect reference tests to define a better reference standard. We call this the composite reference standard (CRS). Using the CRS, accuracy can be assessed using multistage sampling designs. Maximum likelihood estimates of accuracy and expressions for …