Clinical Trial for Evaluation of Vermillion's Blood Test to Predict the Probability of Peripheral Artery Disease (PAD-001)

Peripheral artery disease (PAD) affects 8 to 12 million individuals in the United States and is also prevalent in Europe and Asia. A regional pilot study of community screening for PAD demonstrated that patient awareness of a PAD diagnosis was low, and was associated with atherosclerosis risk factors, antiplatelet therapy, and claudication treatment intensity. PAD has not emerged as a focus of public health efforts to improve quality of life, nor to decrease the associated cardiovascular ischemic risk. Smoking, diabetes, and age are the strongest risk factors for PAD. Smokers have a 2 to 6-fold increased likelihood of having PAD, and the risk of PAD increases in a dose-dependent manner with the duration and amount of smoking. Diabetes confers a 2 to 4-fold increased risk of having PAD. The prevalence of PAD increases as a function of age. Criqui et al showed that the prevalence of PAD in individuals under 60 years of age was about 2.5%, whereas the prevalence increased to over 20% in individuals over 75 years of age.

A study in smokers and diabetics 50 years of age or older, and in all those 70 years of age or older, identified in an outpatient, primary care clinic setting has shown that the prevalence is 29%. About half of the cases found were newly-identified PAD patients. Further, while 83% of those with a prior diagnosis of PAD were aware of their condition, only 49% of the primary-care physicians were aware that their patients had a diagnosis of PAD. Another study examined internal medicine physicians' approaches to PAD and found that only 37% reported taking histories for claudication, and only 26% evaluated the foot for ulcers.

PAD is as prevalent in women as in men. When symptomatic, PAD causes limb discomfort, tiredness, heaviness, cramping, or pain brought on by exertion and relieved by rest (i.e., intermittent claudication) and reduces functional capacity and quality of life. Classic claudication is only noted by 10-30% of patients and atypical leg discomfort occurs in 20-40%. Up to 50% of patients are asymptomatic. PAD1 is an in vitro diagnostic that provides a PAD1 score derived from multiple biomarkers in human plasma, serum, or whole blood, which predicts a low or high probability of the presence of PAD in patients at risk for PAD. A positive PAD1 score(above the cutoff), indicating a higher risk for PAD than expected in the general population, would then guide the physician to more aggressively determine the presence of PAD.

The preliminary studies have shown an association of four proposed biomarkers with ABI, and have demonstrated the construction of a PAD risk algorithm. This study is powered to test each of the four biomarkers and their interactions and develop the PAD1 risk score in the intended use population.