At first, the USPSTF's conclusion may seem surprising. Undiagnosed PAD is common, the ABI has excellent diagnostic and prognostic characteristics, and medications are available that decrease cardiovascular events in persons diagnosed with PAD. Currently, the ABI is used infrequently to screen for PAD in clinical practice in the United States, and the disease is commonly underdiagnosed. The PARTNERS (PAD Awareness, Risk, and Treatment: New Resources for Survival) study measured the ABI of patients in 350 primary care practices across the United States who were aged 70 years or older or aged 50 to 69 years with a history of diabetes mellitus or smoking (7). Of 6979 patients tested, 1865 (29%) had an ABI less than 0.9, which is consistent with PAD. Of note, 45% of those with an ABI less than 0.9 had no history of clinically diagnosed PAD, and only 11% had classic symptoms of intermittent claudication. The remaining participants who tested positive for PAD were asymptomatic or had atypical leg symptoms. These types of PAD were more common among persons newly diagnosed with the disease, suggesting that the high prevalence of asymptomatic disease and atypical leg symptoms contributes to underdiagnosis.