BMJ  2003;327:E21-E24 (4 October), doi:10.1136/bmjusa.01040004 (published 5 September 2002)

BMJ USA: Clinical review

First new screening recommendations from the third US Preventive Services Task Force

Center for Practice and Technology Assessment, Agency for Healthcare Research and Quality, Rockville, MD 20852, USA

Introduction

This article originally appeared in BMJ USA

The US Preventive Services Task Force (USPSTF) is an independent panel first convened in 1984 by the US Department of Health and Human Services to develop evidence-based recommendations for clinicians about preventive health care. The Guide to Clinical Preventive Services, released in 1989¹ and completely revised in 1996,² assessed more than 200 common screening tests, counseling interventions, immunization strategies, and medications for prevention of disease. The primary audience for USPSTF recommendations continues to be clinicians in primary care settings, but many professional societies, health plans and insurers, quality organizations, and policy makers have come to rely on the USPSTF for rigorous and objective guidance about which preventive services should be routinely incorporated into clinical practice.³

The third USPSTF was convened in late 1998 by the Agency for Healthcare Research and Quality (AHRQ). A priority-setting process, which included review by staff and input from outside experts and organizations, found that more than 50 of the 70 chapters in the 1996 Guide were in need of substantial updating; it also identified a number of high-priority new topics. The first new and revised recommendations from the USPSTF resulting from this work, along with summaries of the supporting evidence, have just been released in a special supplement to the American Journal of Preventive Medicine⁴ and on AHRQ's web site (www.ahrq.gov/clinic/uspstfix.htm).

Methods

Detailed descriptions of the methods by which the USPSTF develops its recommendations are available on the USPSTF web site and in the recent supplement.⁵ A number of specific features distinguish the USPSTF recommendations from those of many other organizations. The USPSTF uses an explicit process to define key questions and specify the necessary evidence to establish that a given service is effective. Research teams at two evidence-based practice centers supported by AHRQ develop systematic reviews of the relevant literature (including assessment of the quality of individual studies using objective criteria); these reviews are studied by the USPSTF and by external peer reviewers. The USPSTF then assesses the overall strength of the evidence that a service will improve clinical outcomes, such as disease-specific mortality or morbidity. After estimating the balance of benefits and potential harms (eg, false-positive results, harms of treatment), it votes on a recommendation using grades that are linked to both the quality of supporting evidence and the balance of benefits to harms (table 1). Finally, the recommendations and supporting evidence are circulated widely for comment by content experts, federal agencies, and professional societies.

Key points Recommendations regarding clinical preventive services should consider both quality of supporting evidence and assessment of benefits vs harms. The explicit, evidence-based process used by the US Preventive Services Task Force yields more conservative recommendations about routine screening than are offered by many expert panels. New clinical trials support screening for high blood cholesterol and low HDL levels in women over 45, men over 35, and high-risk young adults, but treatment decisions should consider overall risk of heart disease. Clinicians should routinely screen sexually active women aged 25 and under for chlamydia infection to prevent pelvic inflammatory disease and its complications. Screening for and treatment of bacterial vaginosis during pregnancy are not beneficial in average-risk women but are an option for some women at high risk of preterm delivery. Total body skin examination can improve detection of early skin cancer, but evidence is insufficient to determine whether it will reduce morbidity and mortality from skin cancer.

Table 1. Grades of USPSTF recommendations based on strength of evidence and magnitude of benefits minus harms A. The USPSTF strongly recommends that clinicians routinely provide [the service] to eligible patients. The USPSTF found good evidence that [the service] improves important health outcomes and concludes that benefits substantially outweigh harms. B. The USPSTF recommends that clinicians routinely provide [the service] to eligible patients. The USPSTF found at least fair evidence that [the service] improves important health outcomes and concludes that benefits outweigh harms. C. The USPSTF makes no recommendation for or against routine provision of [the service]. The USPSTF found at least fair evidence that [the service] can improve health outcomes but concludes that the balance of benefits and harms is too close to justify a general recommendation. D. The USPSTF recommends against routinely providing [the service] to asymptomatic patients. The USPSTF found at least fair evidence that [the service] is ineffective or that harms outweigh benefits. I. The USPSTF concludes that the evidence is insufficient to recommend for or against routinely providing [the service]. Evidence that [the service] is effective is lacking, of poor quality, or conflicting, and the balance of benefits and harms cannot be determined.

The first new recommendations from the third USPSTF are summarized below. Complete details of the recommendations, supporting evidence, and complete references are available on the AHRQ web site.

Screening for abnormal lipids in adults

Since 1995, several major trials have confirmed the benefits and safety of lipid-lowering drugs in asymptomatic individuals.⁷ These and other trials have also bolstered the hypothesis that the most important determinant of the magnitude of benefit obtained from lipid reduction is the underlying risk of disease. Newer statin drugs reduce the risk of coronary heart disease (fatal and nonfatal myocardial infarction) by approximately 30% over five years. Although middle-aged men made up most of the subjects in the primary prevention trials, the USPSTF concluded that the benefits of lipid-lowering drug therapy could be extrapolated to other individuals with lipid abnormalities, including postmenopausal women, persons over age 65, persons with low HDL cholesterol levels, and younger adults who might have a risk status comparable to that of middle-aged men because they have multiple risk factors for heart disease or a family history suggestive of familial hyperlipidemia. These revisions narrow the difference between USPSTF recommendations and those of the National Cholesterol Education Program.⁸

Recommendations: screening for abnormal lipid levels in adults6 7 Screen all men ages 35 and older and women ages 45 and older. A recommendation Screen younger persons if they have other risk factors for heart disease. B recommendation Screen for both total cholesterol (or LDL cholesterol) and HDL cholesterol levels. B recommendation No recommendation for or against routine screening of low-risk young adults—benefits likely to be modest. C recommendation

The USPSTF concluded, however, that the proven benefits of screening low-risk young adults were not large enough to justify a strong recommendation: Screening in this group rarely identifies appropriate candidates for drug therapy; outpatient dietary interventions have only modest effects on cholesterol; and screening is not needed to advise young persons of the benefits of reducing dietary saturated fat intake, maintaining healthy weight, and increasing physical activity levels.

Screening for chlamydial infection

Chlamydial infection is the most common sexually transmitted bacterial disease in the United States; it is prevalent among sexually active young women across most demographic groups in the country. Chlamydial infection is associated with long-term complications, such as pelvic inflammatory disease (PID), ectopic pregnancy, and infertility.¹⁰

A high-quality randomized trial demonstrated that screening and treating at-risk women could reduce the incidence of PID by more than 50%.¹¹ A risk score based on a few factors identified a population of at-risk women in whom the prevalence of chlamydial infection was 7%. For every 81 at-risk women invited for screening (and for every 57 women actually tested), one case of PID was prevented over the following year.

The most reliable risk factor for chlamydial infection is younger age. Most studies report a prevalence of chlamydia of 5% or higher for women under 25 and even higher for those under 21. Other risk factors or risk markers associated with higher likelihood of infection include being unmarried, having a new sex partner or multiple sex partners, and being black. The USPSTF noted, however, that existing data come largely from higher-risk settings (family planning clinics, college health centers, etc); if new data indicate that chlamydial infection is less prevalent in more representative community settings, targeted screening may be more efficient in some populations.

The USPSTF could not identify a single best strategy for incorporating factors other than age into screening decisions. Given that there are substantial variations in the prevalence of infection, protocols for identifying at-risk women need to be tested in the specific population in which they will be used. A variety of nonculture tests are now on the market that are sufficiently sensitive and specific for testing for chlamydia using cervical or urine specimens. The choice among them involves tradeoffs in costs, ease of use, and sensitivity and specificity; the optimal test will vary for different settings. The Centers for Disease Control and Prevention is developing a guideline summarizing the advantages and disadvantages of specific chlamydia tests.

Screening for bacterial vaginosis in pregnancy

Bacterial vaginosis (BV) is a common cause of vaginal discharge. It is characterized by an imbalance in the normal vaginal bacterial flora, with a decrease in Lactobacillus spp and an increase in Gardnerella spp, Mycoplasma spp, and anaerobic bacteria.¹³ The presence of BV can be diagnosed by Gram stain or, more commonly, by a collection of clinical criteria, including adherent vaginal discharge, presence of clue cells, low vaginal pH, and an amine odor on addition of KOH to the discharge. Between 9% and 23% of pregnant women may have BV; infection is more common in black than white women. Numerous epidemiologic studies have documented a higher risk of preterm delivery and low–birth-weight infants among pregnant women with BV.

Recommendations: screening for chlamydial infection9 10 Screen all sexually active women aged 25 and under, and other asymptomatic women at increased risk for infection. A recommendation Screen all pregnant women aged 25 and under, and other pregnant women at increased risk for infection. B recommendation Evidence is insufficient to recommend for or against routinely screening asymptomatic men. I recommendation The choice of specific test is left to clinical discretion. Appropriate interval for screening is uncertain.

Recommendations: screening for bacterial vaginosis in pregnancy12 13 Evidence is insufficient to recommend for or against routinely screening for bacterial vaginosis in high-risk pregnant women (ie, women with a previous preterm delivery). Screening is a clinical option. I recommendation Routine screening for bacterial vaginosis in average-risk pregnant women is not recommended. D recommendation

Seven randomized controlled trials have evaluated the effect of various antibiotic treatments versus placebo on pregnancy outcomes among women with bacterial vaginosis.¹³ Among the four studies that reported results for average-risk women, there were no differences between the control and treatment groups in terms of pregnancy outcomes, such as the incidence of preterm delivery or low–birth-weight infants. Further studies are examining the benefits of different treatments in average-risk women.

Four studies reported results of oral antibiotic therapy in high-risk women with a history of preterm delivery. Treatment reduced the incidence of preterm delivery before 37 weeks in three studies^{14 15} that enrolled very high-risk women, but in the largest multicenter trial,¹⁶ which was completed in 1999, oral metronidazole provided no benefit for any group of pregnant women, including high-risk women. Reasons for the conflicting results are not clear but may involve differences in other risk factors for preterm delivery among the enrolled women or differences in the drug regimens and timing of therapy.

Recommendations: screening for skin cancer17 18 Evidence is insufficient to recommend for or against routinely screening for skin cancer using a total body skin examination for the early detection of cutaneous melanoma, basal cell cancer, or squamous cell skin cancer. I recommendation

The USPSTF concluded that the conflicting trial results did not support a clear recommendation for routine screening in any group. Screening might be considered an option in high-risk women, but routine screening in low-risk women should be discouraged outside of ongoing trials. Further undermining a strong recommendation for screening are data from a few studies suggesting that antibiotic treatment in women who do not have bacterial vaginosis may be associated with an increased risk of preterm delivery.¹⁴

Screening for skin cancer

Although the lifetime risk of dying of melanoma is only 1 in 200, the incidence of melanoma has increased almost threefold in the US between 1973 and 1995.¹⁷ Studies of screening among volunteers have found that 1 to 3 per 100 patients has a suspected melanoma, but only 1 to 4 per 1000 screened have a confirmed melanoma.¹⁷ A higher proportion of patients have nonmelanoma skin cancer, but the benefits of early detection are less compelling in this group. A number of studies have demonstrated that screening can detect thinner melanomas (ie, at an earlier stage) than those found during usual care, but there is no direct evidence that screening leads to significant improvements in morbidity or mortality. There is some concern that screening may be more likely to detect less aggressive tumors than to detect more invasive tumors at a more treatable stage.

Next steps and future developments

The USPSTF has focused on several important methodological issues—for example, developing a framework to describe when and how it will incorporate cost-effectiveness analyses into its decisions.¹⁹ In addition, the task force is developing a more detailed approach for considering the efficacy of the broad variety of strategies to deliver counseling and behavioral interventions in the primary care setting (eg, brief advice, group sessions, etc). Further, it is exploring the specific components of counseling that are most effective.

Assessments on more than 20 additional topics—including screening for breast, colon, and prostate cancer; use of hormone replacement therapy; and counseling about physical activity and diet—are in various stages of development and will be released over the next 12 to 18 months. The "Put Prevention Into Practice" program at AHRQ (http://www. ahrq.gov/clinic/ppipix.htm) will develop materials for patients, providers, and policy makers to help disseminate this new work of the USPSTF.

Acknowledgments

The scientific information summarized in this article was prepared by the Evidence-based Practice Centers at Oregon Health Sciences University and Research Triangle Park/University of North Carolina at Chapel Hill, under contract to the Agency for Healthcare Research and Quality. The clinical recommendations are those of the independent US Preventive Services Task Force. No statement in this article should be construed as an official position of the Agency for Healthcare Research and Quality or of the US Department of Health and Human Services.

References

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