Principles and practice of Secondary prevention cost-effective; this explains the popularity of mobile imaging vans that offer full-body computed tomography(CT)and COMMUNITY SCREENING 96 A. Objectives of Screening 196 he direct-to-consumer marketing of genomic analysis. In contrast, many entive medicine alists demand the B. Minimum Requirements for Community Screening same standards of evidence and cost-effectiveness as for 97 . Disease Requirements 197 therapeutic interventions in patients with known disease. A 2. Screening Test Requirements 198 case may be made for even higher standards. Screening 3. Health Care System Requirements 198 means looking for frouble. It involves, by definition, people 4. Application of Minimum Screening Requirements to Spe with no perception of disease, most of whom are well; there- fore great potential exists to do net harm if screening is performed haphazardly. C. Ethical Concerns about Community Screening 199 D. Potential Benefits and Harms of Screening Programs 199 E. Bias in Screening Programs 200 which is the process of searching for asymptomatic diseases F. Repetition of Screening Programs 20 and risk factors among people in a clinical setting (i.e among people who are under medical care). If a patient is for Multiple Diseases(Multiphasic Screening)201 being seen for the first time in a medical care setting, clini cians and other health care workers usually take a thorough H. Genetic Screening 202 medical history and perform a careful physical examination lL. INDIVIDUAL CASE FINDING 202 and, if indicated, obtain laboratory tests. Establishing base A. Periodic Health Examination 202 line findings and laboratory values in this way may produce B. Health Risk Assessments 203 case finding, if problems are discovered, and is considered III. SCREENING GUIDELINES AND “ good medicine” but is not referred to as“ screening RECOMMENDATIONS 203 a program to take annual blood pressure of employees of IV, SUMMARY 204 a business or industry would be considered screening, REVIEW QUESTIONS, ANSWERS, AND EXPLANATIONS ius Thereas performing chest radiography for a patient who w st admitted to a hospital for elective surgery would be called"case finding. The distinction between screening and case finding is frequently ignored in the literature and in practice. Most professional societies do not distinguish between the two in their recommendations regarding screen- Secondary prevention is based on early detection of disease, ing. We use the two terms interchangeably in this chapter through either screening or case finding, followed by treat Chapter 7 discusses some of the quantitative issues involved ment Screening is the process of evaluating a group of in assessing the accuracy and performance of screening, people for asymptomatic disease or a risk factor for develop- including sensitivity, specificity, and predictive value of tests ing a disease or becoming injured. In contrast to case finding In this chapter we assume the reader is comfortable with defined later), screening usually occurs in a communi hese concepts. The purpose here is to discuss broader publi setting and is applied to a population, such as residents of a health issues concerning screening and case finding. Chapter county, students in a school, or workers in an inau Istry. 18 provide n extensive discussion of the u.s. pr reventive Because a positive screening test result usually is not diag- Services Task Force in the clinical encounter. nostic of a disease, it must be followed by a diagnostic test For example, a positive finding on a screening mammogram examination must be followed by additional diagnostic I. COMMUNITY SCREENING g or a biopsy to rule out breast cancer. As shown in Figure 16-1, the process of screening is A. Objectives of Screening complex and involves a cascade of actions that should follow if each step yields positive results. In this regard, initiating a Community screening programs seek to test large numbers screening program is similar to boarding a roller coaster; of individuals for one or more diseases or risk factors in a participants must continue until the end of the process is community setting(e. g, educational, work, recreational)on reached. Many members of the public assume that any a voluntary basis, often with little or no direct financial screening program will automatically be valuable or outlay by the individuals being screened(Table 16-1)
CHAPTER 16 Principles and Practice of Secondary Prevention Negative Record esult Start treatmen treatment reevaluate Positive response Continue treatment Figure 16-1 The pro cess of able 16-1 Objectives of Screening Programs B. Minimum Requirements for Community Screening Programs requirements for establishing a safe, ethical Diseas ive screening program fall into the following ment to prevent Hypertension Disease requirements Screening test requirements infection and a Health care system requirements revent Change in diet and i lea net, an extensive population-wide screening program may be ina propriate. Table 16-2 outlines these requirements in four common screening programs, for hypertension, high choles Behavioral terol, cervical cancer, and ovarian cancer. as further discussed unsafe sexual in Application of Minimum Screening Requirements to Sp practices Environmental Change in occupation Chronic obstructive cific Programs sease from work in a dusty trade L. Disease Requirements Metabolic Elevated seru 1. The disease must be serious(i.e, produce significant mor- bidity or mortality), or there is no reason to screen in the first place. 2. Even if a disease is serious, there must be an effective py for the disease if it is detected of alue unless there is a good chance that detecting the
SECTION 3 Preventive medicine and public health Table 16-2 Requirements for Screening Programs and Ratings of Example Methods to Detect Hypertension, Elevated Cervical Cancer, and O Screening Method and Rating Serum Cholesterol Pap Smear Computed Tomography Requirements Reading(Hypertension) Test(Dyslipidemia)( Cervical Cancer) (Ovarian Cancer) quirements Ettective treatment exists Other diseases or conditions may be detected. est is quick to perfo est is safe Test is acceptable to participants ++++++ Sensitivity, specificity, and other operating Health Care System Requirements meets Case ng in a medical care setting ngs are ap levated cholesterol levels, with total cholesterol measurement based on a rapid screening of blood; cervical cancer, tested by Papanicolaou( Pap)smear; and ovarian cancer, tested by computed tomography(CT) scanning, Ratings are as follows: ++ good; + satisfactory; - unsatisfactory: +/- depends on disease disease in the presymptomatic stage would be followed by Screening for nditions may produce such a effective therapy. Furthermore, the benefits of detecting arge proportion esults that it would not be cost the condition in a few people should outweigh the harms are best sought in the context that occur(and accrue) to people with a false-positive of care. It is possible, however, that screening for some test, including unnecessary, invasive workups and treat- common risk factors, such as elevated cholesterol levels, may ment. For example, at present, there is no value in screen- provide opportunities for education and motivation to seek ing for pancreatic cancer because the chance of cure by care and behavior change. tandard medical and surgical methods is extremely small. The controversy around prostate cancer screening 2. Screening Test Requirements is largely about the benefits of treatment versus the pos sible harm of unnecessary treatment 3. The natural history of a disease must be understood 1. The screening test must be reasonably quick, easy, and clearly enough to know that there is a significant window inexpensive, or the costs of large-scale screening in terms of time, effort, and money would be prohibitive of time during which the disease is detectable, and a cure 2. The screening test must be safe and acceptable to the or at least effective treatment would occur. For example, colon cancer follows an established disease mechan persons being screened and to their clinicians. If the indi from small polyps in the colon to colon cancer. Early iduals to be screened object to a procedure(as frequently detection and surgical removal of a polyp in the colon occurs with colonoscopy), they are unlikely to participate could prevent intestinal obstruction and morbidit and 3. The sensitivity, specificity, positive predictive value,and other operating characteristics of a screening test must be 4. The disease or condition must not be too rare or too known and acceptable. False-positive and false-negative common Screening for a rare disease usually means that test results must be considered. an additional diffie many false-positive test results would be expected for in using screening tests in the general population is that each true finding(see Chapter 7). This increases the cost the characteristics of the screening test may be different and difficulties of discovering persons who truly are ill or in the population screened from the population for whom at high risk, and it causes anxiety and inconvenience for the screening was developed. individuals who must undergo more testing because of false-positive results. Unless the benefits from discovering 3. Health Care System Requirements ne case are very high, as in treating a newborn who has phenylketonuria or congenital hypothyroidism, it is 1. People with positive test results must have access to seldom cost-effective to screen general populations for a follow-up. Because screening only sets apart a high-risk rare group, persons who have positive results must receive
CH AP TER 16 Principles and Practice of Secondary Prevention further diagnostic testing to rule in or rule out actual proportion of cancers can be cured by the time they are disease. Follow-up testing may be expensive, time letected. Because of these problems, community screening onsuming, or painful, with some risk. With many screen for ovarian cancer is not recommended ing programs, most of the efforts and costs are in the For many screening rograms, debate surrounds general follow-up phase, not in the initial screening screening issues such as what age to start the screening, when 2. Before a screening program for a particular disease is how often to repeat the screenin undertaken, treatment already should be available for methods yield accurate results. Screening for breast cancer is people known to have that disease. If there are limited an example of a controversial screening program because the resources, it is not ethical or cost-effective to allow persons benefits seem to be less than originally hoped and risks are with symptoms of the disease to go untreated and yet associated with screening mammography. The age at which screen for the same disease in apparently well persons to begin screening women for breast cancer is particularly 3. Individuals who are screened and diagnosed as having the controversial because breast is less common in disease in question must have access to treatment, or the younger women, but often more aggressive than later in life, process is ethically flawed. In addition to being unethical, and the risks of screening (e.g., false positives)are higher it makes no medical sense to bring the persons screened (Box 16-1) to the point of informing them of a positive test result and then abandon them. This is a major problem for ommunity screening efforts because many people who C. Ethical Concerns about Community Screening ome for screening have little or no medical care coverage. The ethical standards are important to consider when an Therefore, the cost for the evaluation of the positive apparently well population of individuals who have not screening tests and the subsequent treatment(if disease sought medical care is screened In this case the professionals is detected)are often borne by a local hospital or other involved have an important obligation to show that the ben- efits of being screened outweigh the costs and potential risks 4. The treatment should be acceptable to the people being The methods used in performing any public screening screened. Otherwise, individuals who require treatment program should be safe, with minimal side effects d not undertake it, and the accomplished nothing. For example, some men may not want treatment for prostate cancer because of possible D. Potential Benefts and Harms of incontinence and impotence 5. The population to be screened should be clearly defined creening Programs ideologically useful The potential benefits of screening include reduced mortal Ithough screening at"health fairs"and in shopping ity, reduced morbidity, and reassurance. With the goal of enters provides the opportunity to educate the public screening programs to identify disease in the early, presym about health topics, the data obtained are seldom useful tomatic stage so that treatment can be initiated, the potential because the population screened is not well defined and benefits are reduced mortality for many programs. However, tends to be self-selected and highly biased in favor of some screening programs have a goal of early detection using those concerned about their health less invasive treatment(e. g,, taking a small piece of breast 6. It should be clear who is responsible for the tissue rather than removing the entire breast). Another which cutoff points are to be used for consideri potential benefit of screening is the reassurance to both indi result" positive, and how the findings will bec viduals and providers f participants'medical record at their usual plac The potential adverse effects(harms)of all screening pro grams need to be considered. Some screening pr may be uncomfortable, such as mammography, or require 0f ng preparation, such as colonoscopy (colon cleansing). Colon- Specific Pro ograms scopy also carries procedural risks(bleeding, perforation) Table 16-2 applies the previously described criteria to the results, false reassurance for patients with false-negative tests, ollowing four conditions for which community screening and costs to individuals and society from lost work has been undertaken Test errors are a major concern in screening(see Chapter a Hypertension, tested by a sphygmomanometer reading of 7). False-positive test results lead to extra time and costs blood pressure and can cause anxiety and discomfort to individuals whose a Elevated cholesterol levels, based on a screening of blood results were in error. In the case of screening for breast ■ Cervical th papanicolaou cancer, one study showed that the more screening mammo a Ovarian cancer, for which CT scan screening was consid grams or clinical breast examinations given, the more likel ered but rejected one or more false-positive results occurred. An estimated 49%of women who had undergone 10 mammograms had As shown in Table 16-2, screening for hypertension, at least one false-positive reading, equal to a false-positive hypercholesterolemia, and cervical cancer generally fulfill error rate of 6% to 7%on each mammogram the minimum requirements for a community screening False-negative test results can be even worse. Or program. Investigators have agreed that a screening program implied promise made to people is that if they are screened using CT scans to detect ovarian cancer in the general popu- for a particular disease and found to have negative results, lation fails at two critical points. First, the yield of detection they need not worry about that disease. False-negative results is low. Second, as numerous studies have shown, only a sma may lead people with early symptoms to be less concerned
O0 SECTION 3 Preventive medicine and public Health Box 16-1 Screening Controversies: "Are you really saving Lives? And how much worry and lost quality of life Breast cancer and prostate cancer in particular illustrate the chal- the improvement in mortality in women between age 40 and 49 was lenge in weighing evidence of small changes in mortality against side small and that possible harms needed to be considered. Instead, ffects of screening and treatment. Because of the impact of screen- USPSTF recommended that physicians discuss the risks and benefits ing biases, only a change in overall mortality in the screened popula- eening with the women and to proceed according to the tion is considered evidence of an effective screening program. The benefit preferences. This change led to a significant media backlash debate about changes in the U.S. Preventive Services Task Force Many people claimed the decision amounted to"care rationing, and demonstrate that that the USPSTF had overstepped its mandate by weighing mortality few issues in preventive medicine have er to polarize the benefits against anxiety. The Task Force argued that the evidence and health care prof ort a"one size fits all" recommendation and that their guidelines empowered patients and their physicians to make rational Breast Cancer cisions based on evidence and more respectful of individual an io oe resp rematrurelities best cd ne. mnatormuonatemy, truly lead to a saved life; the majority are false-positive findings or lead = As of 2012, the rating is a"B" for women age 50 to 74( nded )and a"C for women 40 to 49, indicating that USPSTF the decision to screen should be individualized, and the net necessary diagnosis and treatment of lesions such as ductal carci is likely small. noma in situ(DCIS), which is not harmful to the majority of women Most women would not have known they had these DCIS lesions Prostate Cancer had it not been for the screening mammography. Women with DCIS re at increased risk for a subsequent diagnosis of invasive breast Prostate cancer affects men in a broad age range and has a wide cancer. Unfortunately, we cannot predict which women with DCIS whereas others are slow-growing and indolent. False-positive will ultimately go on to have invasive breast cancer. Thus, women results of prostate-specific antigen( PSA) testing are common ho are diagnosed with DCIS after a screenIng mammography often undergo breast surgery, chemotherapy, and radiation treatment that and often lead to other unnecessary invasive testing (e. g, biopsy can be costly and traumatic. Similarly, many women whose cancers This testing can then lead to diagnosis(often without a reliable way are detected by mammography still die of their disease. If mammo to distinguish between indolent and aggressive disease), treatment (e.g,surgery, radiation, and/or chemotherapy), and serious harm, mortality in populations screened should decrease. This hypothesis including erectile dysfunction, bladder and bowel incontinence, and death, to manage a disease that might otherwise have never been problematic(most men die with prostate cancer, not of prostate As of 2011, the strongest evidence shows that any difference in To date, the evidence that prostate verall mortality between populations exposed to screenings and cancer screening decreases all-cause or prostate cancer-specific those not screened is small: for every 2000 women invited for screen mortality. If there is any benefit, it likely accrues over more than 10 g throughout 10 years, one will have her life prolonged; 10 healthy years. Therefore, USPSTF advised in 2012 against routine screening omen who would not have been diagnosed if there had not will experience important psychological distress for many months Both these controversies illustrate the need of personalizing screen- because of false-positive findings tate cancer should be based on the patients risk preferences and In 2009, USPSTF changed its screening recommendations regarding willingness to have false-positive test results and invasive follow-up breast cancer for women age 40 to 49, Previously recommending testing. Many decision aids have been developed to help individua routine screening in this population, the Task Force now argued that make informed decisions They may delay medical visits that they might otherwise conducted. An RCT is needed to reduce the potential for have made promptly. False-negative results also may falsely bias In cancer an association between screening and longer reassure clinicians False-negative results can be detrimental survival does not prove a cause-and-effect relationship to the health of the people whose results were in error, and because of possible problems such as selection bias, lead test results delay the diagnosis in people who have an infec tious disease, such as tuberculosis, the screening tests can be Selection bias may affect a screening program in different dangerous to the health of others as well directions, all of which may make it difficult to generalize Overdiagnosis is another potential harm of scree ening findings to the general population. On one hand, individuals programs. For example, screening mammography may lead may want to participate because they have a family history to a diagnosis of a preinvasive lesion that is not invasive of the disease or are otherwise aware that they are at higher breast cancer(see Box 16-1). Actions taken in response to risk of contracting the disease. In this case the screening uch findings, including surgery, may result in a scenario program would find more cases than expected in the general where the ostensible " cure"is in fact worse than the disease. population, exaggerating the apparent utility of screening On the other hand. individuals who are more"health con- E. Bias in Screening Programs scious"may preferentially seek out screening program It is not easy to establish the value of a community screening Lead-time bias occurs when screen ling detects disease
CH AP TER 16 Principles and Practice of Secondary Prevention 20 Disease Occult disease Overt disease Death Rapidly progressive onset (age 60) Lead time D (age 45) (age 50 Slowly progressive (6 cases Figure 16-2 Lead-time bias Overestimation of survival duration among detected cases(relative to those detected by signs and symptoms) detected diagnosis. However, this simply reflects earlier diagnosis, because e overall survival time of the patient is unchanged. From Black WC, Welch HG: Advances in diagnostic imaging and overestimates of disease prevalence and the benefits of therapy, N Eng/ Med 328: 1237-1243, 1993) Test Time o E Time of disease onset DX Time when disease is clinically obvious without testing occurred, so that the period from diagnosis to death is increased. However, the additional lead time(increased time during which diagnosis is known)may not have changed the Figure 16-3 Overestimation of survival duration among screening. natural history of the disease or extended the longevity of detected cases, This is caused by the relative excess of slowly life. This lead-time bias tends to operate in screening fo cases, which are disproportionately identified by screening because the anders, no matter how aggressive the tumors( Fig. 16-2 portional to the le ngth of time during which they are detectable(and thereby inversely proportional to the rate of Length bias occurs when the full spectrum of a particular progression. In these 12 patients, 2 of 6 rapidly progressive cases are tumor, such as prostate cancer, includes cancers that range detected, whereas 4 of 6 slowly progressive cases are detected.(From from very aggressive to very slow-growing Individuals witl Black wC, Welch HG: Advances in diagnostic imaging and overestimates of slow-growing tumors live longer than individuals with the disease prevalence and the benefits of therapy, N Engl Med 328 ive tumors, so they are more likely to be discovered 1237-1243, 1993) by screening. Screening programs often select for the less aggressive, slower-growing tumors, and these patients are ikely to survive longer after detection, regardless of the treatment given(Fig. 16-3) women had an average of four mammograms and five clin Selection, lead-time, and length biases apply to both case cal breast examinations during this decade, and almost one ding and to community screening. Given the potential third had at least one false-positive examination. Recom- oblems in showing the true effectiveness of screening, mending frequent repeat examinations carries a significant great care must be exercised to ensure a community screen- burden of cost and anxiety to rule out disease in individuals ing program is worthwhile with false-positive examinations F. Repetition of Screening Programs G. Simultaneous Screening for Multiple Diseases There are pitfalls carefully considering the details of (Multiphasic So creen repeat screening efforts. This rticularly true if an initial ajor scre reening effort is considered a great success, and Multiphasic s involve screening for a enthusiasm may lead the organizers to repeat the screening variety of diseases in the same individual at one point in too soon(e. g, I year later). Unless the population screened time. Some investigators have argued that multiphasic the second time is very different from the one screened the screening makes community efforts more efficient. when a first time, a screening effort repeated after a short interval is sample of blood is drawn, for example, it is easy to perform ikely to be disappointing. This is because the initial screen a variety of tests, using modern, automated labora ing would have detected prevalent cases(cases accumulated over many years), whereas the repeated screening would However, the yield of multiphasic screening is doubtful detect only incident cases(new cases since the last screen- One problem is that multiphasic screening in an elderly ing), making the number of cases detected in the second population detects many diseases or abnormal conditions screening effort smaller. that have been found earlier and are already being treated, Again, the more screening tests done on an individual, the in which case funds are being used for unnecessary testing. more likely positive findings will occur, both true positive Another problem is that multiphasic screening results in a and false positive. If a woman begins annual breast cancer relatively high frequency of false-positive results, which screening at age 40, she would undergo 30 screening mam- requires many participants to return for more expensive nograms by age 70. One study followed 2400 women age 40 follow-up tests to 69 for a 10-year period to determine the number of mam For each disease-free person screened with a battery of nograms and clinical breast examinations done.' The independent tests(tests that measure different values), the
SECTION 3 Preventive medicine and public health act of genetic test results Table 6-3 Correlation between Number of Screening Tests on patients is often counterir and poorly understood and Persons with False-Positive Result So far, there is little evidence for significant adverse psycho No of Screening Percentage of Persons with at Least logical impact, significant lifestyle changes, or screening Tests Performed One False-Positive Test Resultt adherence from consumer genetic testing. In contrast, prenatal screening has made a significa impact on population health for certain groups. This is par ticularly well established for individuals of Jewish Ashkenazi 18.5% heritage, who have a significant carrier rate of Jewish genet 40.1% For this group, genetic testing combined with careful pretest 72.3% and posttest counseling, has helped couples make informed decisions regarding their family planning. Such testing has The"abnormal"laboratory result, Postgrad Med also led to a decrease in the incidence of certain diseases. Several quality requirements beyond the accuracy of the easure different values (i. e, the tests are independen pErcentages are based on tests that each has a 5% false test are specific to genetic screening tests. The genetic abnor mality found must also correspond to a specific disease or increased risk for disease(clinical validity). Even if probability that at least one of the screening tests would yield detects a genetic abnormality that meaningfully predicts a false-positive finding can be expressed as [1-(1-alpha)"], disease, the information may not be useful to the patient where alpha is the false-positive error rate(see Chapter 7) (clinical utility). For most genetic tests, there is little evi and n is the number of screening tests done. If two screenin dence of clinical utility, and the standards for analytic and tests are performed and alpha is 5% (making the test spec clinical validity are much lower than for any other diagnostic ficity 95%), the probability of a disease-free person's being test. Lastly, genomic screening seems to be predicated on the recalled for further testing is [1-(0.95)]=[1-(0.9025) idea that the only way to change genetic vulnerability is almost 10%. If four tests are performed, the probability is through changing genes. In fact, gene expression is influ 1-(0.95)]=[1-(0.8145)]=18.5%.As Table 16-3 shows, enced by environmental stimuli, and lifestyle intervention if 25 tests are performed, more than 70% of disease-free may change gene expression. individuals would return for unnecessary but often costly One study described a controlled trial of multiphasic I. INDIVIDUAL CASE FINDING creening in which one group of individuals received a battery of special screening tests that included hearing and vision A. Periodic Health Examir nation tests, glaucoma screening, blood pressure measurements, spirometry, electrocardiography, mammography and breast Historically, the most common method of prevention in examination, Papanicolaou smear, chest x-ray film, urinaly clinical medicine, especially for adults, was the annual phy SIS, Con oplete blood count, and 12 blood chemistry tests. sical examination (checkup), now known as the periodi Comparison of the findings in this group with the findings health examination. After World War II the number of avail in a similar control group not subjected to the battery of tests able treatments for chronic illnesses increased greatly, and (but receiving their regular care)found no major differences more people began to have an annual checkup, usually con the health knowledge, mortality rates, or morbidity rates sisting of a medical history, physical examination, complete of the two groups. The group who underwent multiphasic blood count, urinalysis, chest x-ray film, and electrocardio screening, however, spent more nights in the hospital gram. Despite the popularity of these checkups, the number difficult at present to integrate all recommended of recipients was limited because many insurance plans screening tests into a clinical encounter would not cover their costs, although some corporations provided them as a benefit for high-level managers(execu H. Genetic Screening tive physicals"). Most research on the periodic health exami- nation before the 1960s concerned examinations that were Recent advances in genetic testing have made it more and sponsored by businesses or industries or were conducted by more feasible to screen individual patients and populatio he few large health plans existing at the time for many different diseases. Indications for genetic testing An annotated bibliography of 152 early studies of peri may include presymptomatic testing, such as a patient odic health examinations showed that reports published tested for Huntington's disease If the test is positive, patients before 1940 were mostly anecdotal and were enthusiastic are virtually certain of developing the di cr their life- about the examinat Reports between 1940 and 1962 time. Alternatively, testing might be done to establish the were more likely to include quantitative data and, although predisposition for a disease, called susceptibility testing. still supportive, increasingly raised serious questions about his is the dominant form of testing for many common routine use of examinations. The subsequent increase in the diseases, such as coronary artery disease( CAD). Most CAD number of health maintenance organizations(HMOs)in cases follow a multifactorial pattern, with many different turn increased the use of periodic examinations in larger genes interacting with environmental factors to produce populations. Although most investigators agreed that exami- similar disease. For these diseases, the presence or absence of nations in children were beneficial, increasingly the studies particular genetic traits can neither rule in nor rule out that began to cast doubts about the cost-effectiveness of periodic the patient will develop the disease health examinations in adults. 8-
CH AP TER 16 Principles and Practice of Secondary Prevention 203 During the 1970s, investigators began moving toward the The HRAs usually provide a printed report about th idea of modifying the periodic examination to focus or assessed person's relative risk of dying or risk age, combined the conditions and diseases that would be most likely to be with some sort of educational message regarding the types found in a person of a given age, gender, and family history of interventions that would have the most positive effect or This approach was termed lifetime health monitoring, the person's life expectancy, if instituted. The printed HRA he greatest support for a new approach came in 1979, when reports have become more sophisticated in recent years and the Canadian Task Force on the Periodic Physical Examin are sometimes supplemented with individualized educa- tion recommended that the traditional form of periodic tional messages. checkup be replaced by the use of health protection pack Studies have extensively evaluated HRAs, with mixed ages that included gender-appropriate and age-appropriate results. - Criticisms focus on errors or lack of information immunizations, screening, and counseling of patients on a by the persons entering the data, difficulties in validating the periodic basis. Specifically, the Task Force recommended predictions, uncertainties about the correct reference popu that"with certain exceptions, the procedures be carried out lation for baseline risks, and limitations related to the instru- case finding rather than screening techniques; that is, they ments focusing mainly or exclusively on mortality and not hould be performed when the patient is attending for unre- on morbidity or the quality of life. The greatest strength of lated symptoms rather than for a specific preventive purpose. HRAs may be the ability to estimate disease levels at the Among the certain exceptions noted by the task force were population level, clarify how nutritional and lifestyle factors pregnant women, the very young, and the very old, for whom affect an assessed persons risk of death, and motivate the they recommended regular visits specifically for preventive person to make changes in a positive direction. HRAs prin purposes cipally serve to raise awareness, which is just one of several do and generally not the most important, related te B. Health Risk Assessments Health risk assessments(HRAs)use questionnaires or com puter programs to elicit and evaluate information concern I. SCREENING GUIDELINES AND Each assessed person receives information concerning his or RECOMMENDATIONS her estimated life expectancy and the types of interventions that are likely to have a positive impact on health and The many organizations that issue screening guidelines and longevity recommendations include the following For many years, the idea of HRAs has been promoted by clinicians enthusiastic about detecting disease and risk Specialty organizations (e.g, American Ure Actors in individuals. Based on the founders original work, the Society for Prospective Medicine was formed,to a Organizations representing primary care specialties(e.g. improve the construction and use of HRAs and the practice American College of Physicians, American Academy of of preventive(prospective)medicine in a clinical or industrial medical practice. Toward this end, the Society promotes the Foundations for the treatment and prevention of particu- use of HRAs for the following lar diseases(e.g, American Cancer Society) Organizations dedicated to evaluating screening recom Assessing the needs of individual patients as they enter a mendations (e.g, U.S. Preventive Services Task Force medical care system or of employees in an industrial SPSTFI, American College of Preventive Medicine [ACPMI, Canadian Task Force on the Periodic Health Developing health education information tailored to the needs of the individuals who complete the assessment a Developing cost-containment strategies based on better In many cases, these organizations agree on their screen- acquisition of health risk information from individuals ing recommendations. However, certain diseases and screen- ng methods have led to major controversy, such as breast Most HRAs use questionnaires or interactive computer cancer screening and prostate cancer screening. In general, programs to gather data concerning each person being the specialty organizations tend toward recommending ssessed. In addition to data such as height, weight, blood screening methods related to their field, unless there is evi pressure, cholesterol level, and previous and present diseases, dence of harm. In contrast, the ACPM and USPSTF tend to the information usually includes details concerning the per- only recommend screening programs for which there is son's lifestyle and family history. Using an algorithm, a com- unequivocal evidence of benefits puter calculates the person's "risk age" on the basis of the Box 16-2 and Chapter 18.) data. Most HRAs use an algorithm based on findings of the In an effort to clarify many of the issues concerning Imingham Heart Study. The risk age is defined as the age screening and case finding and to make evidence-based rec at which the average individual would have the same risk of ommendations, the U.S. Department of Health and Human dying as the person being assessed. If the assessed persons Services created the U.S. Preventive Services Task Force. It risk age is older than his or her chronologic age, that means its investigations, USPSTF reviews data concerning the effi he or she has a higher risk of dying than the average indi cacy of three broad categories of interventions vidual of the same chronologic age. Likewise, if the assessed person's risk age is younger than the chronologic age, the Screening for disease in asymptomatic clinical popu erson has a lower risk of dying than the average individual lations and in certain high-risk groups (secondary of the same chronologic age prevention)
SECTION 3 Preventive medicine and public health Box 16-2 Lung Cancer Screening: Simulation Models, Stage Differences, and RCTs possibilities.Conducting a randomized controlled trial(RCT) of a CT were then published, with conflicting resu/s, ie ng with helical The development of new diagnostic methods offers new screening curable cancers. Several modeling studies of screen w screening intervention is arduous and time-consuming. In the absence of RCTs, preventive medicine practitioners sometimes rely In 2002 the National Lung Screening Trial was launched. More than studies or mathematical modeling of screening inter 53,000 participants were randomized to either three annual helical through cost-utility analysis(see Chapter 6). The history of CI scans or chest x-ray films. In 2011 the results were published cer screening illustrates the pitfalls of such sources of There were 247 deaths from lung cancer per 100,000 person-years in the low-dose CT group and 309 deaths per 100,000 person-years in Lung cancer remains the number-one cause of cancer mortality in from lung cancer with low-dose CT screening of 20.0%. Although the United States. For a long time, there was no viable way to screen less than expected by proponents, this mortality reduction was still for lung cancer, Chest x-ray and sputum examination had been clinically significant. However, the trial also likely showed evidence tested but only led to more invasive testing, with no difference in of overdiagnosis; even after the gap in detection time between the ortality. Then, helical computed tomography (CT) imaging two screening modalities closed, the screened group had more cancer became available and seemed to offer the capacity to find small lung than the control arm. cancer nodules early. Several uncontrolled trials were perfor and showed higher cancer detection rate. Several authorities advo This example shows that modeling can inform decisions when no cated to start screening immediately based on the difference in the evidence is available. However, given the significant biases at work distribution of cancer stages found in the screened group from that to have uncontrolled studies overestimate screening benefits, there is usually found in clinical practice; patients in the screened group were no alternative to rigorous rCts luch more likely to be diagnosed with early and small, potentially Counseling to promote good health habits and prevent ndividuals for the specific set of conditions and diseases disease(health promotion) most likely to be found in persons of a certain age and n Immunizations and chemoprophylaxis to prevent spe- gender, and its use has been advocated by experts on preven cific diseases(primary prevention tive medicine in Canada and the United States. Many prac- titioners who emphasize preventive medicine prefer to see The first report of the USPSTF was issued in 1989. Since their patients for checkups more often than may be recom then, there have been regular literature reviews and updated mended, such as I or 2 years, to maintain a relationship of creening recommendations for the entire spectrum of di trust and to repeat health promotion messages that are eases amenable to screening, counseling, and prophylaxis. important for efforts to change behavior Recommendations are upgraded regularly and are available References ⅣV. SUMMARY I. Berwick DM: Screening in health fairs: a critical review of benefits, risks, and costs. JAMA 254: 1492-1498, 1985 2. Nelson HD et al: Screening for ovarian cancer: a brief update The goal of secondary prevention is the detection of disease http://www.uspreventiveservicestaskforce,org/3rduspstf/ or risk factors in the presymptomatic stage, when medical ariancan/ovcanup. htm. environmental, nutritional, and lifestyle interventions can be 3. Nelson HD, Tyne K, Naik A, et al: Screening for breast cancer: most effective. Screening is done in a community setting, an update for the U.S. Preventive Services Task Force. Ann whereas case finding is done in a clinical setting. To be ben stern Med151:727-737,2009 eficial and cost-effective, community screening programs 4. Elmore JG, Armstrong K, Lehman CD, et al: Screen must fulfill various requirements on the health problem to breast cancer. JAMA 293: 1245-1256, 2005 be detected, the screening test used, and the system available JD 77-84,1976 to provide health care for people with positive screening 6. Christopherson WM, Parker JE, Drye )C: Control of cervical results. Selection, lead-time, and length biases can lead to cancer:preliminary report on a community program. JAMA overestimates of benefit from screening, particularly the 182:179-1 program detecting cancer. Although multiphasic screening 7. Elmore JG, Barton MB, Moceri VM, et al: Ten-year risk of false seeks to make the process efficient by searching for ma positive screening mammograms and clinical breast exami conditions at the same time, the high incidence of fals tions. N Engl J Med 338: 1089-1096, 1998. positive results and associated problems have made this tech 8. Bates B, Yellin JA: The yield of multiphasic screening. JAMA nique less successful than was originally anticipated. Genetic 222:74-78,1972 screening introduces a new subset of requirements for 9. olsen dm, Kane rl proctor ph: a controlled trial of multi screening tests, including clinical validity and clinical utilit hasic screening. N Engl J Med 294: 925-930, 1970 10. Yarnall Ks, Pollak Kl, Ostbye T, et al: Primary care: is there Historically, the periodic health examination has been the most common method of case finding. Because of disap enough time for prevention? Am J Public Health 93: 635-641 pointing benefits, however, it is now being replaced by life- 11. Robin NH, Tabereaux PB, Benza R, et al: Genetic testing in timehealth monitoring This approach focuses on monitoring cardiovascular disease. J Am Coll Cardio! 50: 727-737, 2007
CHAPTER 16 Principles and Practice of Secondary Prevention 205 2. Heshka JT, Palleschi C, Howley H, et al: A systematic review of 29 reServicesTaskForce.http://www.uspreventive erceived risks, psychological and behavioural impacts of netic testing. Genet Med 10: 19-32, 2008 30. US Preventive Services Task Force: Guide to clinical preventive 3. Bloss CS, Schork N], Topol E]: Effect of direct-to-consumer vices, ed 2, Baltimore, 1996, williams wilkins nome-wide profiling to assess disease risk. N EnglJ Med 31. When evidence collides with anecdote, politics, and emotions breast cancer screening. Ann Intern Med 152: 531-532, 2010 14. Gross S]: Carrier screening in individuals of Ashkenazi Jewish 32. Gotzsche PC, Nielsen M: Screening for breast descent. genet Med 10: 54-56. 2008 mammography. Cochrane Database Syst Rev(1): CDo01877 15. Hogarth S, Javitt G, Melzer D: The current landscape for direct- to-consumer genetic testing: legal, ethical, and policy issues. 33. Chou R, Croswell JM, Dana T, et al: Screening for prostate Annu Rey Genomics Hum Genet 9: 161-182. 2008 cancer: a review of the evidence for the u.s. Preventive services 16. Ornish D, Magbanua MI, Weidner G, et al: Changes in prostate Task Force. Ann Intern Med 155: 762-771. 2011 lifest expression in men undergoing an intensive nutrition and 34. Kramer BS, Berg CD, Aberle DR, et al:Lu ith low-dose helical CT: results from the National Lung Screening Trial. J Med Screen 18: 109-111, 2011 17. Siegel GS: Periodic health examinations: abstracts from the 35. The National Lung Screening Trial: overview and study design erature, Washington, DC, 1963, US Department of Heal NLST Research Team. Radiology 258: 243-253, 2011 36. Henschke CI: CT screening for lung cancer is justified. Nat Clin 18. Schor SS, Clark Tw, Parkhurst Lw, et al: An evaluation of the Pract Onco/ 4: 440-441, 2007. periodic health examination: the findings in 350 examinee 37. Mahadevia PJ, Fleisher LA, Frick KD, et al: Lung cancer screen who died. Ann Intern Med 61: 999-1005, 1964 19. Roberts NJ, Ipsen J, Elsom KO, et al: Mortality among males in a decision and cost-effectiveness analysis. JAMA 289 313-322, periodic health examination programs. N Engl J Med 281: 20- 38. Bach PB, Jett JR, Pastorino U, et al: Impact of com Brown BP: Unanswered questions about the peri- aphy screening on lung cancer outcomes. JAMA 297: 1-9, examination. Ann Intern Med 83: 257-263, 1975 21. Breslow L, Somers AR: The lifetime health monitoringproi Med 39. National Lung Screening Trial Research Team: Reduced lung a practical approach to preventive medicine. N Engl J Med cancer mortality with low-dose computed tomographic screen 296:601-608,1977 22. Canadian Task Force on the Periodic Physical Examination: 40. Sox HC: Better evidence about screening for lung cancer The periodic health examination Can Med Assoc/121: 1193- N Engl/ Med 365: 455-457, 2011 23. Robbins LC, Hall J: How to practice prospective medicine, Ind napoli, 1970, Methodist Hospital of Indiana. Select reading 24. Society for Prospective Medicine: Managing health care, me: Fletcher RH, Fletcher SW: Clinical epidemiology: the essentials, ed 4 appraisal. Thirty-First Annual Meeting of the Sociely lor A K ring lives: expanding the definition and scope of health Philadelphia, 2005, Lippincott, Williams wilkins spective Medicine, New Orleans, 1995 based medicine: fundamental principles of clinical reasoning and 25. Foxman B, Edington DW: The accuracy of health risk appraisal in predicting mortality. Am J Public Health 77: 971-974, 1987 research. Thousand Oaks, Calif, 2001, Sage. health risk appraisal(editorial).Am Welch HG: Should I be tested for cancer? Maybe not and here's wh / Appraising Berkeley, Calif, 2004, University of California Press Public health 77: 409411.1987 Woolf SH, Jonas S, Kaplan-Liss E, editors: Health 27. Smith Kw, McKinlay SM, McKinlay )B: The reliability of health disease prevention in clinical practice, ed 2, Phila risk appraisals: a field trial of four instruments. Am J Publie Heaith79:l603-1607,1989 28. ODon A simple framework to describe what Website skills, viding opportunity. Am J Health Promot http:/wwwuspreventiveservicestaskforce.org/[u.S.Preventive suppl): 1-7(following 84, iii), 2005 Services ta
