BENEDICT I. TRUMAN STEVEN M. 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 more intensive or profound change in a subgroup of the population, usually within selected settings (e.g., workplace, hospital or clinic, place of worship, or school). We use the same logic to distinguish between "community-wide screening" and "screening in the community."
Screening for disease is defined as the examination of asymptomatic members of a defined community to classify them as either likely or unlikely to have the target disease or health condition. Persons who appear likely to have the target disease are referred for definitive diagnosis and treatment (Morrison 1992). Persons who appear unlikely to have the disease are educated to be vigilant for early warning signs and symptoms and encouraged to seek early diagnosis and treatment, if necessary. Educating persons who have "normal findings" may positively influence future health behaviors and encourage follow-up by primary care providers (Mittelmark et al. 1993).
Early detection and effective treatment are expected to result in substantial reductions in morbidity, mortality, and disability from targeted health conditions in a screened population. For example, screening for early detection and treatment of hypertension has contributed to an estimated 50% reduction in age-adjusted mortality from stroke in the United States since 1972 (National High Blood Pressure Education Program [NHBPEP] 1993; Garraway and Whisnant 1987; Casper et al. 1992). Similarly, early detection by mammography (with or without clinical breast exam ) and effective treatment of breast cancer are expected to reduce mortality rates by as much as
30% over >10 years in a screened population of women 50-69 years of age (U.S. Preventive Services Task Force [USPSTF] 1996).
In addition to its role as a population-based prevention strategy, screening for selected target conditions is equally important as a clinical preventive service. Primary care practitioners, during a clinical visit for episodic health care, can deliver this service to asymptomatic persons of all ages and in all risk categories (USPSTF 1996). This screening strategy also is referred to as "case-finding" or "in reach" (Sackett et al. 1991; Lantz et al. 1995). Screening of persons and of populations is expected to play an important role in the attainment of the year-2000 national health promotion and disease prevention objectives (US Dept of Health and Human Services [USDHHS] 1991). For example, mortality objectives have been set for coronary heart disease; cancers of the breast, cervix, colon, and rectum; and other conditions for which screening is relevant. Progress toward achieving year 2000 objectives for mortality and related screening-procedure uptake is being monitored and publicized by means of annual reports (National Center for Health Statistics [NCHS] 1996b). For example, the rate of death among women from breast cancer (age adjusted per 100,000 US standard population in 1970) has declined from 23.0 in 1987 to 21.6 in 1993, nearing 20.6 (the year 2000 target). In addition, the proportion of females >50 years of age who have received clinical breast examination and mammogram in the preceding 1-2 years has increased from 25% in 1987 to 55% in 1993, nearing the year 2000 target of 60%.
In recent years, screening has been more commonly associated with the control of chronic conditions such as heart disease (e.g., blood pressure and cholesterol), cancer (e.g., mammography, Pap test, and testicular examination), and congenital abnormalities (screening among newborns). However, important applications of screening for the prevention and control of infectious diseases have a long history and current importance in traditional public health practice. For example, the US Preventive Services Task Force (USPSTF) has recommended selective screening in high risk populations for several infectious conditions (e.g., human immunodeficiency virus [HIV], tuberculosis, chlamydia, rubella, syphilis, and gonorrhea) in the context of a clinical periodic health examination (USPSTF 1996). As with chronic conditions, early detection and treatment of cases of infectious disease improves the clinical outcome of persons affected by disease. In addition, early detection and successful treatment of infectious diseases interrupts transmission of infection to other members of the community (Morrison 1992).
The integration of screening at the individual, setting, and community levels can be illustrated conceptually (Figure 7-1). At the individual level, health care providers interact with patients in a clinic to address their needs for preventive services (e.g., vaccinations, counseling to encourage health-promoting behaviors, and screening for selected health conditions). The community liaison, based in the clinic, "reaches in" to encourage patients receiv
ing care to use available preventive services and "reaches out" into a specific community setting to help persons who are not receiving care to gain access to the preventive services they need. In each community setting (a place of worship, workplace, or school), health promotion and disease prevention goals are pursued in collaboration with clinicians and other health-related institutions. Health departments, universities, managed-care plans, the media, and other institutions provide leadership and support for community-wide interventions to promote health and prevent disease.
This chapter reviews basic concepts and principles associated with (1) screening to control disease; (2) adopting and implementing practice guidelines on screening; and (3) developing, implementing, and evaluating public health screening programs.
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