Screening for Diseases: Prevention in Primary CarePDF
ACP J Club. 2005 Jan-Feb;142:A11. doi:10.7326/ACPJC-2005-142-1-A11
Clinicians who offer screening tests bear a heavier responsibility than do those consulted by patients who are, or believe themselves to be, ill. Most patients who accept the screening offer derive no benefit because they are true negatives, whereas persons with false-positive or false-negative results are harmed in the process. This dilemma is made clear by David Eddy in a classic introductory chapter to the American College of Physicians' update to their 1991 bestseller, Common Screening Tests.
The new book, Screening for Diseases: Prevention in Primary Care, contains 5 U.S. Preventive Services Task Force (USPTF) reviews of screening programs that were published in Annals of Internal Medicine (type 2 diabetes, postmenopausal osteoporosis, breast cancer, colorectal cancer, and prostate cancer) and 2 commissioned pieces on screening for depression and hypertension. Also included are 2 chapters dealing with preventive strategies (hormone replacement therapy [HRT] for cardiovascular disease and aspirin for cardiovascular disease). The justification for inclusion of these interventions is that primary chemoprophylaxis should be considered similar to screening as a prerequisite to an effective intervention. The authors argue that recommending HRT and aspirin in otherwise-healthy patients to prevent cardiovascular disease is analogous to screening for the diseases and then offering interventions. As with the tests, most persons taking the drugs would not have had the vascular events they seek to prevent. Similar processes are used to find, critically appraise, and present the current evidence base to those used for diagnostic tests. The nature of the intervention, groups to be targeted, outcomes, and costs are all considered before summarizing the current state of knowledge for both.
The book was commissioned by the U.S. Agency for Health Care Policy and Research in 1998. The work was conducted by several highly skilled teams using the well-documented, methodologically rigorous techniques of the USPTF. It is targeted at internists, residents, and health care practitioners; however, patients and policymakers would also benefit from reading it. Although the literature review is comprehensively international, it simply underscores the absence of evidence from many populations beyond Europe and North America.
Each chapter is preceded by a set of summary points and the main text follows Eddy's advice on how to think about screening by going back to clear, basic principles and the original papers (typically 150 references per chapter). The passages dealing with screening tests will be particularly useful to policymakers and clinicians who wish to provide evidence-based guidelines on outcomes and costs. The bottom-line number needed to screen (NNS) is provided for a variety of outcomes in each chapter where possible. Sensitivity analyses based on prevalence, age, and other relevant risk factors are presented in tables. In some conditions, such as prostate cancer, no benefits have been shown, only costs, so it is currently impossible to derive an NNS for specific beneficial outcomes. All studies that contribute to the meta-analyses are graded for quality, and the reasons for adopting or discarding the evidence provided by the major studies are well described. The final 2 pages contain a table summarizing the current recommendations for selected preventive services for adults.
Could the book be better? Well, an index would be nice.
Frank Sullivan, PhD, FRCP, FRCGP
University of Dundee
Dundee, Scotland, UK
Methods/Quality of Information: 5 of 5 stars
Clinical Usefulness: 5 of 5 stars
Screening for Diseases: Prevention in Primary Care can be purchased at www.acponline.org/catalog/books/prevention.htm?acp3293 for U.S. $40 (ACP members: U.S. $36)