Confounding Effect Modification Bias Confounding

A variable that is a known or suspected cause of the outcome under study (or is a surrogate for cause) and is also statistically associated with the exposure of interest is a confounding variable. Formally, a confounding variable may be defined as a variable that is causally related to the condition under study independently of the exposure of primary interest, and is associated with the exposure of primary interest in the study population, but is not a consequence of the exposure. Because of...

Communication and Media Considerations

Perhaps more important than many of the scientific issues concerning outbreak and cluster investigations, effective communication is a key component of the investigation process. Data are not useful to the public and to other scientists unless findings are convincingly communicated (King 1991). Essential ingredients of successful communication of information to a scientific audience have been outlined by others (Gregg 1996b) and are summarized in Chapter 11. Communication is often necessary...

Acquire Tools and Clearances for Collection Analysis and Dissemination

Before establishing any surveillance system, whether an emergency assessment during a field investigation or a process of continued monitoring for months or years to come, the public health practitioner should first be very clear about the legal aspects of such a plan. In most instances, surveillance is conducted under the aegis of state health laws or regulations, rather than federal legislation. In epidemic investigations, the field team is usually given oral approval for setting up emergency...

Successes of Epidemiology and Public Health

The accomplishments of epidemiology, public health, and related social changes have changed the pattern of death and disease in modern society. Infant mortality in the United States has fallen from 150 per 1,000 live births in 1900 to 8.5 per 1,000 in 1992 (Taylor et al. 1993 National Center for Health Statistics 1996a). Life expectancy from birth has risen from 47 years in 1900 to more than 75 years in 1992 (National Center for Health Statistics 1996a). This represents an increase of over 2...

Scope and Definitions of Epidemiology

Epidemiology is often considered the basic science of public health. This pivotal role was emphasized by the Institute of Medicine in its definition of public health as organized community efforts aimed at the prevention of disease and promotion of health. It links many disciplines and rests upon the scientific core of epidemiology (Committee for the Study of the Future of Public Health 1988). Since the 1920s, several dozen definitions of epidemiology have been advanced (Lilienfeld 1978). A...

Estimating Sample Size

Although it is important to assure that a study has adequate statistical power in order to avoid erroneous conclusions resulting from inadequate sample size, it is inefficient to include more study subjects than are needed. Furthermore, a study that is too large may declare as statistically significant an effect that is so small in size that it is biologically and clinically meaningless. Determining the optimal sample size for a study is one of the most important aspects of study planning....

Summary

This chapter provides a contemporary overview of issues relevant to practitioners as they design, implement, and evaluate screening programs. To facilitate their application, key concepts and principles were grouped under each of four operational tasks that practitioners must accomplish to be successful. Thus, concepts of community, settings, mass versus selective screening, risk stratification, and high-risk versus population strategy are important in defining the target population for...

Cluster Investigations

Clustering of disease has intrigued public health professionals for many years and some cluster investigations have led to important scientific discoveries. For example, the investigation of spatial clustering of enamel discoloration early in the twentieth century led to discovery of the relation between flouride levels in drinking water and dental caries (Rothman 1987). Another notable cluster investigation led to the epidemiologic discovery that clustering of vaginal cancer was linked with...

Cost Benefit Analysis Versus Other Types of Economic Evaluation

In cost-benefit analysis all of the consequences of interventions are valued in monetary terms. For example, in a cost-benefit analysis of renal dialysis, a dollar value is assigned to a life saved by providing this treatment. In a cost-benefit analysis of a worksite injury reduction program, a dollar value is placed on the pain and suffering prevented by the program. Assigning a monetary value to human life or to pain and suffering is a difficult task. There are several ways it can be done....

The Importance of Applied Epidemiology

Throughout its history, epidemiology has provided a basis for understanding the underlying causes of many diseases and health conditions. A variety of analytic tools and statistical methods have been developed (Kelsey et al. 1996), resulting in a better understanding of etiology. This knowledge of causes has fostered the development of applied epidemiology, which can be defined as the application and evaluation of epidemiologic discoveries and methods in public health and health care settings....

Statistical Issues in Outcomes Research Risk Adjustment and Predictive Modeling

Most outcomes research studies are nonexperimental. Although these studies take advantage of natural experiments, the possibility that differences in outcomes might be due to differences in patients' characteristics or factors other than the intervention or unit of care cannot be dismissed. Risk adjust ment aims to take confounding into account. When outcomes research involves the comparison of the effectiveness of an intervention in one or more groups of patients, risk adjustment is directly...

The Evolution of Risk Assessment

The formal characteristics of risk assessment have a brief history (NRC 1994a Rodricks 1992). While many core concepts had been developed earlier, the origins of contemporary risk assessment can be traced to the 1970s when new environmental regulations called for information on risks in order to set policy. Even earlier, however, the need to protect the general public and workers had led to the development of methods for setting exposure limits that inherently involved risk estimation. To...

Euro Qol Quality of Life Scale Euro Qol

The EuroQol (EuroQol Group 1990 Essink-Bot et al. 1993) was developed beginning in the late 1980s by a multinational group. The goal of the group was development of a simple measure of general health that would provide a single index value of health status. The 1993 version of the EuroQol covers five dimensions of health mobility, self-care, usual activities, pain discomfort, and anxiety depression. Respondents rate themselves in each one of three mutually exclusive categories (no problem, some...

Measuring and Communicating Weak Associations

Quantitatively, a weak epidemiologic association is one in which the estimate of relative risk (often in the form of an odds ratio) is less than 3 (Wynder 1987). The abilities to assess weak associations with validity and to appropriately communicate epidemiologic findings to the public are continuing challenges for modern epidemiology. Epidemiology has had great success in identifying the origins (and magnitude) of many public health epidemics. Examples include cigarette smoking lung cancer,...

Measuring Life Expectancy

Life expectancy is defined by actuaries as the average future lifetime of a person. It is usually estimated for persons of a specific age, sex, and race. Actuarial methods to estimate life expectancy are based on specialized statistical lifetable functions that rely on data on mortality rates specific for age, sex, and race. The age-, sex-, and race-specific mortality rates are based on death certificate data and census data. In very rare cases, life expectancy for interventions has been...

Quality of Well Being Scale QWB

The QWB (Kaplan and Anderson 1988) assesses health status by asking about symptoms and level of function in three areas mobility, physical activity, and social activity. These ratings are linked with weights that were derived from a general population sample to yield a single index, scaled from 0.0 to 1.0, that represents a judgment about the social undesirability of the overall problem. Unlike the SIP and the SF-36, the scaled QWB values can used in economic analysis to estimate...

Experimental Studies

In general, experimental studies provide the strongest evidence that a given exposure is the cause of a disease or other condition or that a preventive or therapeutic intervention is effective. In experimental studies, the investigator randomly assigns individuals or another unit e.g., community, school, clinic either to be exposed or not exposed to an intervention and then follows them through time to determine the outcomes of interest. Randomization attempts to create comparability on factors...

Defining the Target Population

Defining the target population for a screening program involves describing the settings and the characteristics of the collection of persons who would be eligible for screening Last 1995 . This should be the first step in planning a population-based screening program because screening programs should be tailored to meet the needs of a defined target population. In practice, however, screening programs are developed and implemented in response to the availability of an effective screening test...

Differing Perceptions of Voluntary and Involuntary Risks

Individuals react differently to health risks that are imposed voluntarily e.g., lack of physical activity compared with those acquired involuntarily, often as the result of advancing technology e.g., a nuclear power plant Starr and Whipple 1980 . In general, individuals and society have been more willing to accept voluntary risks than involuntary risks. The methods for quantitative risk assessment outlined in Chapter 5 can lead to a more rational basis for risk evaluation. Despite the...

Expert Panels and Expert Review

Virtually every government agency, in both executive and legislative branches, utilizes expert panels or expert review when examining epidemiologic studies and their relevance to health policies. The main goal of expert panels is to provide peer review i.e., using scientific experts to review the quality of the science and scientific interpretations that underlie health policy decisions. When conducted well, peer review can provide an important set of checks and balances for the regulatory...

Epidemiologic Challenges in Cluster Investigations

Several of the difficulties encountered in cluster investigations parallel those discussed earlier for investigations of outbreaks and occupational clusters others are more applicable to cluster studies due to their noninfectious nature. Limitations have been summarized by several researchers CDC 1990 Roth-man 1990 Neutra 1990 . Rothman 1990 has suggested that there is little scientific or public health purpose to investigate individual disease clusters at all. While it is likely that...

Study Designs

Epidemiologic studies can be broadly categorized as either observational or experimental. In observational studies, relationships are studied as they occur in nature. In experimental studies, the investigator intervenes and studies the effects of the intervention. Observational studies have two fundamental objectives to describe the occurrence of disease or disease-related phenomena and to explain them. Studies attempting to identify the causes of disease are generally called analytic...

Matching and Stratification

Communities can be allocated to treatment groups within pairs, as in COMMIT Gail et al. 1991 and the Minnesota Heart Health Program Jacobs et al. 1986 , or within strata, as in the Kaiser Community Health Promotion Grants Program Wagner et al. 1991 and the Child and Adolescent Trial for Cardiovascular Health CATCH , which allocated schools Zucker et al. 1995 . The advantages of doing so are potential reductions in bias and gains in precision. Bias may be reduced because both techniques render...

Screening in the Community

Public Health Nursing Pictures

TEUTSCH Screening for disease in the community to promote health and prevent disease is one of the practical applications of epidemiology delineated by Terris and reiterated in Chapter 1 of this text. Green and Kreuter 1991 distinguish a community intervention from an intervention in a community. A community intervention is community-wide and aims to achieve a small but pervasive change in most of the population. An intervention in a community aims to accomplish...

Types of Economic Evaluation

Most authors O'Brien 1995 Epstein and Sherwood 1996 describe four main types of economic valuation cost-minimization analysis, cost-benefit analysis, cost-effectiveness analysis, and cost-utility analysis. The assumption and questions addressed in these four kinds of economic evaluation are summarized briefly in Table 9-1. There is substantial overlap between the types of studies shown in Table 9-1. Cost-minimization analysis, cost-benefit analysis, and cost-effectiveness analysis all compare...

Contributors

Andy Amster, MSPH Care Assessment and Improvement Kaiser Permanente Medical Care Program Southern California Region Pasadena, California Department of Community Health School of Public Health Saint Louis University St. Louis, Missouri Thomas A. Burke, PhD Department of Health Policy and Management School of Hygiene and Public Health The Johns Hopkins University Baltimore, Maryland Jennifer L. Kelsey, PhD Division of Epidemiology Stanford University School of Medicine Palo Alto, California Abby...

The Role of the Epidemiologist in Health Policy Making

Epidemiologists have numerous opportunities for influencing the development, implementation, and evaluation of health policies. An epidemiologist may affect health policy by conducting and disseminating their own research, commenting on others' research to the media or in other public settings, serving on advisory groups that make policy recommendations expert panels , serving as an expert witness in litigation, testifying before a policymaking body e.g., city council or state legislature , or...

Choosing Effective Screening Tests

Screening in the community for a priority health condition depends on the availability of a screening test that is reliable, accurate, acceptable to participants i.e., patients and clinicians , and affordable in relation to its benefits Wilson and Jungner 1968 Morrison 1992 . Thus, screening for breast cancer is feasible because mammography, an effective screening test, is available. However, screening for lung cancer an equally important health condition is considered infeasible because...

Analysis Based on Community Means

One way to avoid violation of statistical independence assumptions is to aggregate individual-level observations to the community level and then use the community-level means or proportions as the primary data to be analyzed. This approach follows the classic Fisherian advice to analyze as you randomize Fisher 1935 . It is a simple and valid method for study designs in which the number of individuals studied per community is approximately the same across communities. The main test of...

Methods for Combining Studies Metaanalysis Basis of Metaanalysis

Because the results of any one study of an issue are seldom definitive, it is often useful to combine results from many studies. Meta-analysis, described in detail by Petitti 1994 , Dickersin and Berlin 1992 , and Greenland 1987 , is one approach to combining results. Specifically, meta-analysis is a quantitative approach for systematically combining the results of previous research in order to arrive at conclusions about the body of research as a whole Petitti 1994 . Petitti describes four...

Descriptive Studies

Descriptive studies provide information on the frequency of occurrence of a particular condition and on patterns of occurrence according to such attributes as person, place, and time. Routinely collected statistics from such sources as mortality data, hospital discharge records, general health surveys, and disease surveillance programs are used for most descriptive studies see Chapter 4 . Characteristics related to person often include age, gender, race, ethnicity, marital status, socioeconomic...

Ross C Brownson

Health policies, in the form of laws, regulations, and organizational practices, have a substantial impact on the health and well-being of the population. Policies can influence one or more of the following 1 modifiable causes of disease, 2 early detection of disease in asymptomatic persons, 3 disease treatment in persons with symptomatic disease, and 4 rehabilitation and recovery. Formulation of health policies often depends on scientific, economic, social, and political forces Terris 1980...

Diana B Petitti Andy Amster

The measurement and improvement of quality of care have been a part of health care for decades. Recently, attempts to measure and monitor quality have become more intense as a response to demands for accountability in the delivery of services Relman 1988 and as an outgrowth of the quality and outcomes movement. The development of systems to measure the performance of organizations that deliver health care is a part of the attempt to assure accountability. It is also a response to consumer...

The Community Approach and Practice Guidelines for Health Policy Development

As epidemiologic findings are translated into health policies, the process becomes both an art and a science. Successful policy development and implementation involves many disciplines and audiences, including epidemiologists, behavioral scientists, public information and media specialists, policy analysts, and policy makers. The translation of epidemiology into health policy has been outlined in different frameworks Figures 12-3 and 12-4 . While none of these fits every situation, they do...

Measuring Quality Structure Process Outcome

Quality of care can be measured based on structure, process, or outcome Donabedian 1980, 1982,1985 . Structural measures are the characteristics of the resources in the health system. For providers, these variables include professional characteristics e.g., specialty, board certification . For institutions, they include size, location, ownership, and licensure status, as well as physical attributes e.g., number of beds, ownership and other organizational factors e.g., staff-to-patient ratios ....