LEVELS OF PREVENTION

Basically, leading a healthy life contributes to the preven­tion of disease. There are three fundamental types of pre­vention: primary prevention, secondary prevention, and tertiary prevention²⁸ (Chart 1-2). Primary prevention is di­rected at keeping disease from occurring by removing all risk factors. Immunizations are examples of primary pre­vention. Secondary prevention detects disease early when it is still asymptomatic and treatment measures can affect a cure. The use of a Papanicolaou (Pap) smear for early detection of cervical cancer is an example of secondary prevention. Ter­tiary prevention is directed at clinical interventions that pre­vent further deterioration or reduce the complications of a

CHART 1-2

Levels of Prevention

• Primary prevention: Actions aimed at prevention of

disease

• Secondary prevention: Actions aimed at early

detection and prompt treatment of disease

• Tertiary prevention: Treatment and rehabilitation

measures aimed at preventing further progress of the disease

disease once it has been diagnosed. An example is the use of β-adrenergic drugs to reduce the risk for death in persons who have had a heart attack. Tertiary prevention measures also include measures to limit physical impairment and social consequences of an illness.

Primary prevention often is accomplished outside the health care system. Chlorination and fluoridation of water supplies and laws that mandate seat belt use are examples of community-wide primary prevention. There are fewer community-wide efforts directed at secondary prevention, and those that are available usually do not involve the en­tire community. Examples include breast self-examination education programs and blood pressure screening programs. Nevertheless, many health care clinics are becoming in­creasingly devoted to primary and secondary prevention through such activities as prenatal and well-child care, im­munizations, lifestyle counseling, and screening for early disease detection or risk factors. There are many fewer ter­tiary prevention efforts outside the health care system.

EVIDENCE-BASED PRACTICE AND PRACTICE GUIDELINES

Evidence-based practice and evidence-based practice guide­lines have recently gained popularity with clinicians, pub­lic health practitioners, health care organizations, and the public as a means of improving the quality and efficiency of health care.²⁹,³⁰ Their development has been prompted, at least in part, by the enormous amounts of published in­formation about diagnostic and treatment measures for various disease conditions as well as demands for better and more cost-effective health care.

Evidence-based practice has been defined as "the con­scientious, explicit, and judicious use of current best evi­dence in making decisions about the care of individual patients."²⁹ It is based on the integration of the individual expertise of the practitioner with the best external clini­cal evidence from systematic research.²⁹ The term clinical expertise implies the proficiency and judgment that in­dividual clinicians gain through clinical experience and clinical practice. The best external clinical evidence relies on the identification of clinically relevant research, often from the basic sciences, but especially from patient-centered clinical studies that focus on the accuracy and precision of diagnostic tests and methods, the power of prognostic indicators, and the effectiveness and safety of therapeutic, rehabilitative, and preventive regimens.

Clinical practice guidelines are systematically devel­oped statements intended to inform practitioners and clients in making decisions about health care for specific clinical circumstances.³¹,³² They not only should review various outcomes but also must weigh various outcomes, both positive and negative, and make recommendations. Guidelines are different from systematic reviews. They can take the form of algorithms, which are step-by-step meth­ods for solving a problem, written directives for care, or a combination thereof.

The development of evidence-based practice guide­lines often uses methods such as meta-analysis to combine evidence from different studies to produce a more precise

estimate of the accuracy of a diagnostic method or the ef­fects of an intervention method.³³ It also requires review: by practitioners with expertise in clinical content, who can verify the completeness of the literature review and ensure clinical sensibility; by experts in guideline development who can examine the method by which the guideline was developed; and by potential users of the guideline.³¹

Once developed, practice guidelines must be continu­ally reviewed and changed to keep pace with new research findings and with new diagnostic and treatment methods. For example, the Guidelines for the Prevention, Evaluation, and Treatment of High Blood Pressure (see Chapter 25), first developed in 1972 by the Joint National Committee, have been revised seven times, and the Guidelines for the Diag­nosis and Management of Asthma (see Chapter 31), first de­veloped in 1991 by the Expert Panel, have undergone three revisions.

Evidence-based practice guidelines, which are intended to direct client care, are also important in directing research into the best methods of diagnosing and treating specific health problems. This is because health care providers use the same criteria for diagnosing the extent and severity of a particular condition such as hypertension and because they use the same protocols for treatment.

In summary, the health of individuals is closely linked to the health of the community and to the population it encom­passes. Epidemiology is the study of disease in populations. It looks for patterns such as age, race, and dietary habits of per­sons who are affected with a particular disorder to determine under what circumstances the particular disorder will occur. Using epidemiologic methods, researchers determine how a disease is spread, how to control it, how to prevent it, and how to eliminate it.

Epidemiologists use measures of disease frequency to pre­dict what diseases are present in a population and as an indi­cation of the rate at which they are increasing or decreasing. Incidence is the number of new cases arising in a population during a specified time. Prevalence is the number of people in a population who have a particular disease at a given point in time or period.

Morbidity and mortality provide epidemiologists with in­formation about the functional effects and death-producing characteristics of a disease. Mortality or death statistics provide information about the trends in the health of a population. Morbidity describes the effects an illness has on a person's life. It is concerned with the incidence of disease as well as its per­sistence and long-term consequences.

Conditions suspected of contributing to the development of a disease are called risk factors. They may be inherent to a person (high blood pressure) or external (smoking). Studies used to determine risk factors include cross-sectional studies, case-control studies, and cohort studies. Cross-sectional studies use the simultaneous collection of information necessary for classification of exposure and outcome status. Case-control studies are designed to compare subjects who are known to have the outcome of interest (cases) with those who are known not to have the outcome of interest (control). Cohort studies involve groups of persons who were born at approximately

the same time or share some characteristic of interest. The Framingham Study, which examined the characteristics of people in whom coronary heart disease would later develop, and the Nurses' Health Study, which initially explored the re­lationship between oral contraceptives and breast cancer, are two well-known cohort studies.

The natural history of disease refers to the progression and projected outcome of a disease without medical intervention. It can be used to determine disease outcome, establish priori­ties for health care services, provide direction for prevention and early detection programs, and compare treatment meth­ods and their outcomes with untreated outcomes. Prognosis is the term used to designate the probable outcome and prospect of recovery from a disease.

The three fundamental types of prevention are primary prevention, secondary prevention, and tertiary prevention. Pri­mary prevention, such as immunizations, is directed at re­moving risk factors so that disease does not occur. Secondary prevention, such as a Pap smear, detects disease when it still is asymptomatic and curable with treatment. Tertiary preven­tion, such as β-adrenergic drugs to reduce the risk for death in persons who have had a heart attack, focuses on clinical in­terventions that prevent further deterioration or reduce the complications of a disease.

Evidence-based practice and evidence-based practice guide­lines are mechanisms that use the current best evidence to make decisions about the health care of individuals. They are based on the expertise of the individual practitioner in­tegrated with the best clinical evidence from systematic re­view of credible research studies. Practice guidelines may take the form of algorithms, which are step-by-step methods for solving a problem, written directives, or a combination thereof.