International ABI awareness as the next step in the PAD campaign

Peripheral artery disease (PAD) is common, underdiagnosed, and undertreated. Owing to the systemic nature of atherosclerosis, PAD patients are at risk for polyvascular disease. For example, 63% of patients with PAD have concomitant symptomatic cerebrovascular or coronary disease. ¹ Accordingly, PAD patients are at significantly increased risk for myocardial infarction, stroke, and vascular death over a 5-year period compared to age-matched cohorts.

The ankle–brachial index (ABI) is the preferred initial test for PAD screening and diagnosis. It is relatively inexpensive, sensitive, and specific. Current guidelines provide clear recommendations on the indications for ABI testing.^2,3 However, these guidelines may not have been fully implemented among practitioners.

In this issue of Vascular Medicine, Haigh and colleagues investigate several issues related to PAD awareness among general practitioners (GPs) in Queensland, Australia. ⁴ They examine the prevalence of PAD screening as well as the most commonly used tools for both screening and diagnosis of PAD. Finally, they address barriers to screening and the use of the ABI. Data were collected by a cross-sectional mail-out survey to 1120 GPs. Among these, 232 qualified for analysis.

Fortunately, GPs were aware that PAD is common and associated with increased cardiovascular mortality. However, respondents tended to overestimate the mortality and amputation rates, particularly among symptomatic PAD patients. GPs rated asymptomatic PAD as less serious than symptomatic PAD. One major strength of the study is that the survey distinguishes between PAD screening and PAD diagnosis, which are two distinct but important issues. A strikingly low 6% of GPs were aware of evidence-based guidelines on PAD screening, and only 5% were aware of guidelines on PAD diagnosis. The majority of GPs (58%) never perform ABIs. Most notably, 70% of the respondents choose arterial duplex (which is more costly and time-consuming) as the initial diagnostic tool in a patient with a history and physical exam consistent with PAD; younger GPs were more likely to choose the ABI.

The most common ‘moderate to major’ barriers to PAD screening and testing were (1) equipment availability, (2) time constraints, (3) lack of training and skills, and (4) staff availability. The time constraint barrier is not surprising, given that the time for an ABI could approach the 15-minute length of a typical primary care office visit. Other studies have also identified limited reimbursement and time as primary barriers to widespread use of the ABI in primary care practices. ⁵

The study by Haigh et al. has several limitations. First, the response rate was low at 26%. Among the initial 287 responses, 55 (19%) were excluded because the GPs reported not consulting with PAD patients, which is unusual given how common PAD is in primary care. The remaining sample size of 232 is relatively small. In spite of these limitations, the study clearly highlights the importance of disseminating PAD guidelines and improving ABI awareness. Overcoming such barriers as limited time and equipment is difficult, but, at the very least, we should be able to educate practitioners on an international level that the ABI is the best initial test to diagnose PAD.

Lack of knowledge regarding which test to order and confusing ultrasound terminology can be major obstacles for referring providers. Our vascular laboratory often receives a request for a ‘Doppler’ without further specification as to which body part or whether it should be an arterial or venous study. Or an arterial duplex is ordered when physiologic testing is clearly the more appropriate diagnostic test. Non-invasive physiologic testing, when added to the ABI, provides additional information regarding the location and severity of PAD. Physiologic testing may include segmental limb pressures, continuous wave Doppler tracings, or pulse volume recordings.

Acronyms abound and vary among institutions, from NIFS (Non-Invasive Flow Studies) in New York City to LENIS (Lower Extremity Non-Invasive Studies) in Boston and LEAFS (Lower Extremity Arterial Flow Studies) in Chicago. Selecting the appropriate test requires an inquisitive scheduler, an astute vascular technologist, and/or a conscientious medical director in the vascular laboratory. Fortunately, the Intersocietal Accreditation Commission and its accreditation process help to facilitate quality of care among vascular laboratories. But deciphering these vague vascular testing requests can be an onerous task.

Major gaps in public knowledge in the United States were found in the first national PAD public awareness survey published in 2007. ⁶ ‘Stay in Circulation’ was developed by the National Heart, Lung, and Blood Institute in cooperation with the PAD Coalition, a group of more than 40 national organizations and professional societies concerned with raising awareness. Since then, this public health campaign and clopidogrel advertisements together have succeeded in adding PAD to the lexicon among many patients. Yet this study highlights that knowledge gaps still persist among practitioners. Hands down, the ABI is the most useful non-invasive test to detect PAD. Perhaps the first step towards improving PAD diagnosis is to continue to send a consistent international message that the diagnostic approach to PAD begins with a simple ABI.

Meanwhile, the debate continues as to the mortality benefit of ABI screening among asymptomatic populations, and as to whether third party payers will ultimately fund this screening. In September 2013, the United States Preventive Services Task Force (USPSTF) recently issued an ‘I’ recommendation for ABI screening, concluding that current evidence is insufficient to assess the balance of its benefits and harms. ⁷ The ‘I’ designation represents a change from the ‘D’ rating in 2005, which recommended against it. Importantly, the USPSTF notes that large, population-based, randomized trials are needed to determine whether ABI screening improves outcomes. In contrast to the USPSTF, the American College of Cardiology and the American Heart Association practice guidelines recommend the ABI in patients at risk (aged 65 or older; or aged 50 or older with a history of diabetes or smoking) and in patients with exertional leg symptoms or non-healing wounds.

Regardless of the guidelines on ABI screening, there is no debate that a patient with symptoms and risk factors needs to be tested for PAD with an ABI, perhaps along with physiologic testing if clinically indicated. A large percentage of symptomatic patients with PAD remain undiagnosed, and international efforts should focus on educating GPs on the diagnostic approach to PAD. Australia may lead the way in this endeavor: their National Health and Medical Research Council (equivalent to the US National Institutes of Health) has funded a National Centre for Research Excellence to improve the management of PAD. ⁸

In conclusion, this study provides important insights on current screening and diagnostic practices among GPs. This study is the first of its kind to be conducted in Australia, and the results are in line with prior international studies which have also highlighted the related gaps and barriers. Now that we have raised PAD awareness among patients, the next critical step in the campaign should be raising international ABI awareness among practitioners.