Background: Resting ankle-brachial index (ABI) is the first-line diagnostic test for lower extremity peripheral artery disease (PAD). Previous studies that reported high sensitivity and specificity (often >90%) of ABI included only clinically diagnosed PAD cases and non-PAD controls, overestimating measurement accuracy of ABI relative to unselected populations. A community-based study observed sensitivity of ~20%, but only included older adults aged around 70 years. Objective: To assess the validity of resting ABI to detect PAD among community-based adults and evaluate whether the addition of other tests (post-exercise ABI, toe-brachial index TBI, and two types of waveforms pulse volume recordings (PVR) and continuous Doppler) can improve the diagnostic accuracy. Methods: We used data from the PAD Study of Study of Latinos (PASOS; 2020-24). Resting ABI and TBI were measured on each side. PVR waveforms were recorded using air plethysmography with ankle cuffs; continuous Doppler waveforms were assessed at the ankle and dorsum of the foot using a Doppler probe. Then, post-exercise ABI was measured after heel raises, performed 50 times or up to 2 minutes. We compared the validity of resting ABI ≤0.9, ≤1.0, and a comprehensive multi-modal definition: (1) resting ABI ≤0.9, (2) a post-exercise ABI drop ≥20% or an ankle blood pressure drop ≥30 mmHg, or (3) at least two abnormalities of TBI, abnormal PVR, and abnormal continuous Doppler waveforms. We considered arterial diameter reduction ≥50% or systolic peak velocity ≥200 cm/s in Duplex ultrasound as stenosis. Results: Among 405 participants (mean age 63.4 SD 8.1 years; 64.2% female), there were 70 cases of PAD based on ultrasound detection of leg artery stenosis. ABI ≤0.9 alone showed a sensitivity of 17.1% and specificity of 96.7%, with Youden’s index of 0.14 ( Figure ). Using ABI ≤1.0 as the threshold for PAD, sensitivity reached 48.6% but specificity went down to 66.8%, with an unchanged Youden’s index of 0.15. The multi-modal approach had a sensitivity of 50.0% and specificity of 84.1%, with Youden’s index of 0.34. The results were largely consistent in the subset of high-risk group (n = 312). Conclusions: ABI ≤0.9 alone had a sensitivity of <20% for detecting PAD among middle-aged and older adults in the community, whereas additional modalities markedly improved the overall diagnostic accuracy. Our results have implications on strategies for PAD screening in the community.
Cao et al. (Tue,) studied this question.