August 2020

Diagnostic Accuracy of PADnet Xpress® in the Detection of Peripheral Artery Disease

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By Sue Duval, PhD

With existing knowledge, much of the cardiovascular risk burden of peripheral artery disease (PAD) is preventable. PAD is a common atherosclerotic syndrome that is estimated to affect 12.5 million Americans and 237 million people worldwide.1 One in five Americans over the age of 65 has PAD.2 Based on national treatment patterns, more than half of all patients with PAD do not know they have it. Left undetected and untreated, PAD significantly increases the risk of cardiovascular events, such as myocardial infarction and stroke, and adverse limb events, including the need for revascularization, amputation, or both.

The ankle-brachial index (ABI) is the standard diagnostic test for peripheral artery disease (PAD). ABI is the ratio of the systolic blood pressure at the ankle to the systolic blood pressure in the arm.

The major risk factors for PAD are a history of smoking, diabetes, older age, high blood pressure, high blood cholesterol, alcohol use, obesity, and a family history of PAD. Left untreated, PAD can lead to stroke, heart attack, and/or amputation and has a five-year mortality rate of over 30%.3

The latest iteration of PADnet is the PADnet Xpress®, featuring technology designed for the front lines of care and configured in an easy-to-use, quick, portable, and secure form factor to enable medical assistants to perform studies where there may not be direct access to vascular specialists.

Methods

Patients

In a recent study, 180 patients (314 segments) were assessed for PAD using both PADnet Xpress and physiologic testing in various settings including primary care, office-based vascular/endovascular labs, ambulatory surgery centers, and hospitals.

Reference test: Physiologic Testing

Patients received physiologic testing, including ABIs and Pulse Volume Recordings (PVRs). In some instances, angiography or ultrasound was also performed and clinical notes and observations recorded. In those cases, a Registered Vascular Technologist analyzed the observations and notes and classified disease accordingly. An ABI between 0.9 to 1.35 was considered normal, 0.41 to 0.89 mild to moderate, and severe 0 to 0.4.

Index test: PADnet Xpress

The predictive algorithm associated with PADnet Xpress is designed to mirror the numeric values generated by the ABI. The researcher conducting the index test was blinded to the outcome of the reference test.

Results

The prevalence of an abnormal test in the sample was 44% (78/180). With the reference test as the gold standard, the study results confirmed excellent diagnostic accuracy of the PADnet Xpress with sensitivity of 90% and specificity of 68%.

Conclusions

Given the sensitivity and specificity results as well as portability, speed-of-test, and ease-of-operation, PADnet Xpress appears to be well suited for in-home and in-clinic PAD assessments. Combined with the Biomedix Xchange population health platform, PADnet Xpress should enable cost-effective care protocols to be more easily and securely realized, and most importantly, may improve patient outcomes. The approach of early detection and implementation of effective therapies has the potential to improve debilitating walking impairment and prevent cardiovascular events in millions of people with PAD.

Sue Duval, PhD, is Associate Professor of Medicine and Biostatistics at the University of Minnesota Medical School and School of Public Health in Minneapolis, Minnesota. Her current research and consulting portfolio includes peripheral artery disease, critical limb ischemia, vascular surgery, resuscitation science, and meta-analysis.

REFERENCES
  1. Song P, Rudan D, Zhu Y, Fowkes FJI, Rahimi K, Fowkes FGR, Rudan I. Global, regional, and national prevalence and risk factors for peripheral artery disease in 2015: an updated systematic review and analysis. Lancet Glob Heal [Internet]. 2019;7:e1020–e1030. Available from: http://dx.doi.org/10.1016/S2214-109X(19)30255-4
  2. Diehm C, Allenberg JR, Pittrow D, Mahn M, Tepohl G, Haberl RL, Darius H, Burghaus I, Trampisch HJ. Mortality and vascular morbidity in older adults with asymptomatic versus symptomatic peripheral artery disease. Circulation. 2009;120:2053–2061.
  3. Criqui MH, Langer RD, Fronek A, Fiegelson HS, Klauber MR, McCann TJ, Browner D. Mortality over a period of 10 years in patients with peripheral arterial disease. NEJM. 1992;326:381–386.

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