Abstract Body: 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.