Optimizing ankle-brachial index measurement for peripheral arterial disease screening in mobile clinics

Objective

Multidisciplinary mobile clinics (MMCs) provide a robust venue to provide health care access and peripheral arterial disease (PAD) screening to underserved populations. The ankle-brachial index (ABI) can facilitate PAD diagnosis; however, traditional supine ABI measurements may be challenging technically in a mobile outreach clinic with limited infrastructure, whereas seated ABI offers technical ease. In this study, the usefulness and feasibility of performing supine ABI, seated ABI, and seated ABI with a calculation to account for seated hydrostatic pressure (seated-adjusted ABI) were compared in a mobile outreach setting.

Methods

Prospective data were collected from patients at five independent MMCs focused on diabetic foot and PAD screening with ABI for underserved communities. Three techniques were used to measure the ABI: seated ABI, seated-adjusted ABI using a formula to account for hydrostatic ankle pressure, and traditional supine ABI using a foldable massage table that is 5% of the cost of a medical stretcher. Comparative analysis was performed using the Student t test analysis and one-way analysis of variance. The frequency of completed seated ABI, seated-adjusted ABI, and supine ABI examinations performed at independent MMCs was quantified to determine feasibility.

Results

In 166 individuals experiencing homelessness or housing instability who were screened over the course of five MMCs, 89 underwent PAD screening with ABI. Of the patients screened, 38 patients had seated, seated-adjusted, and supine ABIs measured (43% of total number of patients undergoing any ABI measurement). PAD (ABI < 0.9) was identified in one patient using all three ABI methods. Noncompressible ABI (ABI ≥ 1.3) were identified in 32 patients (32/38 [84%]) screened with seated ABI. Of these 32 patients, 24 (75%) continued to have noncompressible ABIs using seated-adjusted ABI. Of these 24 patients, 4 (17%) continued to have noncompressible ABI using supine ABI. The average seated ABI significantly differed from supine ABI (1.34 vs 1.14; P < .0001). The average seated ABI also significantly differed from seated-adjusted ABI (1.34 vs 1.29; P = .026). The average seated-adjusted ABI significantly differed from supine ABI (1.29 vs 1.14; P = .0204).

Conclusions

We found that seated and seated-adjusted ABI are grossly inaccurate and more often lead to falsely elevated noncompressible ABI (32/38 [84%] and 24/38 [75%], respectively) compared with supine ABI (6/38 [16%]). We recommend using supine ABI on patients for PAD screening. Supine measurement is technically feasible in outreach mobile clinics using a transportable folding massage table and is a more accurate tool for PAD screening.