(Circulation. 2006;114:861-866.)
© 2006 American Heart Association, Inc.
Special Report |
From the Cardiovascular Division (J.A.B., M.A.C.), Brigham and Womens Hospital, Boston, Mass; and the Division of Cardiovascular Medicine (M.R.J.), Massachusetts General Hospital, Boston, Mass.
Correspondence to Joshua A. Beckman, MD, Cardiovascular Division, 75 Francis St, Boston, MA 02115. E-mail jbeckman{at}partners.org
| Abstract |
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Key Words: peripheral vascular disease diagnosis tests mortality atherosclerosis
| Introduction |
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One method by which AHRQ carries out its mission is by issuing practice guidelines developed by the United States Preventive Services Task Force (USPSTF). As described on the AHRQ web site, "the USPSTF (is) the leading independent panel of private-sector experts in prevention and primary care. The USPSTF conducts rigorous, impartial assessments of the scientific evidence for the effectiveness of a broad range of clinical preventive services, including screening, counseling, and preventive medications. Its recommendations are considered the gold standard for clinical preventive services."1 In fact, "the mission of the USPSTF is to evaluate the benefits of individual services based on age, gender, and risk factors for disease; make recommendations about which preventive services should be incorporated routinely into primary medical care and for which populations; and identify a research agenda for clinical preventive care." Thus, as the arm of the AHRQ responsible for the determination of appropriate clinical practice, interested in persuading patients, providers, and payers to adopt its recommendations, the influence of this agency is significant. It is in this context that the recent USPSTF update of the "Recommendation Statement on Screening for Peripheral Arterial Disease (PAD)" is disappointing.2 The USPSTF assigned routine screening of PAD a "D" recommendation, suggesting that the USPSTF minimally determined that PAD screening is ineffective or that the harm of testing outweighs the benefits. We suggest that a more complete review of the literature and careful evaluation would lead to a recommendation in favor of PAD screening. We present evidence that refutes the statements conclusion, providing a clinical framework that supports routine, office-based screening for PAD.
The USPSTF asks 5 Key Questions to determine the value of a PAD screening test. Specifically, they ask:
| USPSTF: Flawed Assumptions |
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| Evidence of High Diagnostic Yield in Targeted Primary Care Screening |
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70 years of age or persons aged 50 to 69 years with a history of cigarette smoking or diabetes were screened by an ABI in the physicians office. Of the 6979 subjects who were screened, PAD was detected in 29%.7 Among those with PAD, 44% had PAD alone without other significant manifestations of atherosclerosis. It is important to note that patients with PAD were less well treated with risk factormodification therapies than were patients with other forms of atherosclerosis. In the German Epidemiological Trial on Ankle Brachial Index (GETABI study), 344 primary care practitioners across Germany screened 6880 consecutive patients 65 years or older.8 PAD was found in 19.8% of men and 16.8% of women. Finally, in the National Health and Nutrition Examination Survey (NHANES), 1999 to 2000, of 2174 free-living persons, the prevalence of PAD in the United States was estimated at 5 million persons, with 14.5% of the population >70 years of age affected.9 Each of these studies makes clear that PAD is common in primary care practice and that the diagnosis is easily established by use of the ABI in well-defined populations. These studies, among many others, effectively rebut the USPSTF statement about the data that were readily available for review, as they concluded that "no new evidence... was identified" for Key Question 2.
Whereas we agree that, like any arbitrary testing strategy, indiscriminate PAD screening would be unlikely to provide benefit, we support targeted PAD screening for high-risk patients (defined as individuals <50 years of age with diabetes and one other atherosclerosis risk factor; individuals 50 to 69 years of age with a history of smoking or diabetes; individuals
70 years of age; those with leg symptoms with exertion (suggestive of claudication) or ischemic rest pain; and those with an abnormal lower-extremity pulse examination), as recommended by the American College of Cardiology/American Heart Association PAD Guidelines.4
More interesting, perhaps, is the contention by the USPSTF that "nearly 75% of those with PAD are asymptomatic" and the lack of attention that point receives. In the PARTNERS study described above, 10% of the PAD population had classic claudication (symptoms of muscular ischemia brought on by walking). However, 50% of the PAD subjects had other leg symptoms, a finding that has been reported in all PAD surveys. The prevalence of arthritis, lumbar spine disease, and venous insufficiency is high in these age groups and may either contribute to functional disability or obscure a patients description of leg ischemic symptoms. PAD patients with atypical leg symptoms also have impaired walking ability when compared with patients without PAD.10 However, atypical leg symptoms do not now lead to prompt ABI testing. On the basis of observational data, approximately 10% of the Medicare population with PAD would be undiagnosed. In fact, nearly 90% of all PAD patients would be missed if ABI testing were withheld from patients without classic symptoms and those with atypical leg symptoms.
The most important omission of the USPSTF statement, however, is the failure to incorporate the increased risk of cardiovascular death in its report. Because it is impossible to reduce limb morbidity in patients who have not complained of symptoms, most vascular disease experts recommend the generalized screening of patients for PAD because of the increased risk of death and the evidence supporting the use of medical therapies to reduce adverse outcomes.11 Twenty years ago, Widmer and Biland12 reported a 37% mortality rate at 11 years in patients with PAD. Epidemiological studies have demonstrated a strong relation between decreasing ABI and death.13,14 Even asymptomatic patients with PAD have 10-year mortality rates as high as 40%.15 In the Limburg Peripheral Arterial Occlusive Disease Study, the 7-year mortality rate was 10.9% in patients without PAD, compared with 25.8% in patients with asymptomatic PAD and 31.2% in those with symptoms.16 Indeed, in a systematic review of the literature that included studies that used an ABI cutoff between 0.80 and 0.90 to classify patients with PAD, followed patients prospectively, and recorded cardiovascular outcomes, the presence of a low ABI more than doubled the risk of coronary heart disease, more than doubled the risk of stroke, and more than quintupled the risk of cardiovascular death.17 Thus, absence of symptoms neither defines a "risk-free" population nor results in freedom from cardiovascular events.
| Rationale for Screening: Ischemic Event Reduction |
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In our opinion, the principal goal of screening for PAD is not to improve walking distance in patients whose symptoms are minimal or absent but rather to reduce the risk of major cardiovascular morbidity and mortality. The USPSTF fails to consider the data demonstrating that atherosclerotic riskmodifying therapies reduce mortality rates in patients with PAD. The USPSTF acknowledges the importance of smoking cessation and states "... counseling for smoking cessation... should be offered to all patients who smoke, regardless of the presence of PAD." This statement indicates misunderstanding of the time course of risk, which is distinctly different between the general population and individuals with PAD. In an era in which access to tobacco cessation resources is constrained and the benefits of treatment could be amplified, identification of high-risk groups is merited. In addition, for Key Question 4, the USPSTF found only one cross-sectional study to demonstrate the benefits of statin treatment for asymptomatic individuals with PAD.19 The Task Force also stated that there was no association with the outcome measures and other treatments, such as aspirin or angiotensin-converting enzyme (ACE) inhibitors. The recently published Heart Protection Study confirmed the benefits of cholesterol lowering in patients with PAD.20 Before this study, and amplified by these study results, the National Cholesterol Education Program guidelines from the Adult Treatment Panel III declared that the PAD-associated ischemic event risk is equivalent to the risk associated with coronary artery disease and therefore requires aggressive reduction in total and low-density lipoprotein cholesterol.21 Patients with PAD require reduction in low-density lipoprotein cholesterol similar to patients with coronary heart disease, a goal that is not required for a patient without known atherosclerosis. This mandate is also now included in the peer-reviewed PAD Guidelines. The Task Force makes no mention of the need for reduction in blood pressure to goal levels as established by the Joint National Committee VII Report.22 A prospective, multicenter, randomized trial found that modification of the reninangiotensin system with an ACE inhibitor ameliorates the major cardiovascular events among patients with PAD.23 The use of antiplatelet therapy is a cornerstone of therapy for patients with established atherosclerosis. Compelling evidence indicates that antiplatelet therapy reduces adverse cardiovascular events such as myocardial infarction, stroke, and death in patients with PAD.24,25
An important unanswered question is the potential benefit of screening in terms of effectiveness (Figure). Three parameters shape the potential benefits of screening: disease prevalence, event rates, and the benefit accrued with therapy. The first parameter has been well defined by the PARTNERS and other related cross-sectional studies: For every 100 patients
70 years of age or between 50 and 69 years of age who smoke or have diabetes, 29 patients will have PAD. The second parameter has been defined by several large epidemiological studies. In the 4 most recent large studies, PAD mortality rates range from 3.9% to 8.2% per year.16,2628 Recently, Feringa and colleagues27 have reported the efficacy of cardioprotective pharmacotherapies in 2420 patients with PAD to provide insight into the third parameter. Over a median follow-up period of 8 years, 44% of the cohort died. In multivariate analysis adjusted for all baseline clinical variables, use of a statin reduced mortality rates by 54%, use of a ß-adrenergic blocker reduced mortality rates by 32%, use of aspirin reduced mortality rates by 28%, and use of an ACE inhibitor reduced mortality rates by 20%. Thus, according to the estimates noted above, the approximate reduction in mortality rates may range from 2 to 9 lives saved per 100 patients screened over the course of 7 years of follow-up, assuming a 25% to 50% mortality rate reduction with the institution of appropriate therapy (Figure). In contrast, the USPSTF estimated that screening in men 65 to 74 years of age who smoked >100 cigarettes in their lifetimes would save 1 life for every 500 patients screened over a period of 5 years.18 It becomes hard to reconcile the abdominal aortic aneurysm and PAD USPSTF statements with a direct comparison of potential benefit. The establishment of the diagnosis of PAD in asymptomatic patients and institution of appropriate therapies should offer reductions in cardiovascular morbidity and mortality and a conclusion opposite to that reported by the USPSTF in Key Question 4.
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| Rationale for Screening: Symptomatic Improvement |
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| PAD as a Cardiovascular Public Health Priority |
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The National Institutes of Health, through the National Heart, Lung, and Blood Institute, has undertaken several initiatives that underscore the importance of diagnosis and management of vascular diseases, especially PAD. First, it has sponsored clinical research grants in PAD.32 Second, it has created funding opportunities to increase the number of training programs for specialists in this area.33 Finally, it is partnering with a coalition of more than 40 specialty professional societies and health advocacy groups, the PAD Coalition (www.padcoalition.org), to create a national public awareness campaign to increase the national appreciation of the risks of PAD.34 Each of these initiatives recognizes the central fact of PAD in the United States and internationally: It is underappreciated, underdiagnosed, and undertreated.
| Conclusion |
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| Acknowledgments |
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None.
| Footnotes |
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| References |
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