What is the difference between single-level and multiple-level Ankle Brachial Index (ABI) measurements?

From the Guidelines

The ankle-brachial index (ABI) should be measured at multiple levels to provide a more comprehensive and accurate diagnosis of peripheral arterial disease (PAD), as it allows for the localization of disease, distinction between single-level and multilevel disease, and characterization of arterial occlusive lesions. The ABI is defined as the ratio between the higher of the brachial artery pressures and the higher of the dorsalis pedis or posterior tibial artery pressures in each leg at the level of the ankle 1. While single-level ABI measurements can be useful for screening purposes, they have limitations, such as not allowing the localization of disease or distinction between single-level and multilevel disease 1.

Key Points to Consider

• Multiple-level ABI measurements provide more detailed information about the location and severity of arterial stenosis, helping to pinpoint where blockages exist in the arterial tree 1.
• Segmental pressure measurements (SPMs) compare systolic pressures at sequential levels in the extremities to evaluate for significant drops between one level and the next, allowing for the distinction between single-level and multilevel disease 1.
• Pulse-volume recordings (PVRs) provide a qualitative measurement of limb perfusion, which can be useful in patients with noncompressible vessels, and can help characterize arterial occlusive lesions 1.
• The use of multiple-level ABI measurements is particularly valuable for patients with calcified vessels, such as those with diabetes or kidney disease, where single-level ABI may give falsely elevated readings 1.

Clinical Implications

• Multiple-level ABI measurements are preferred for comprehensive evaluation, especially before planning interventions or when diagnostic clarity is needed 1.
• The results of multiple-level ABI measurements can help guide treatment decisions, such as the need for further imaging or intervention 1.
• The use of multiple-level ABI measurements can improve patient outcomes by providing a more accurate diagnosis and guiding appropriate treatment 1.

From the Research

Ankle Brachial Index Single Level vs Multiple Levels

• The ankle-brachial index (ABI) is a widely used non-invasive test to assess peripheral arterial disease (PAD) in patients with leg pain on walking that is alleviated by rest 2.
• A systematic review found that the accuracy of ABI in detecting significant arterial disease on angiography is superior when stenosis is present in the femoropopliteal vessels, with sensitivity of 97% and specificity of 89% for oscillometric ABI 2.
• The US Preventive Services Task Force (USPSTF) found insufficient evidence to assess the balance of benefits and harms of screening for PAD with the ABI in asymptomatic adults 3.
• A population-based study found that community-dwelling patients with severe PAD or poorly compressible arteries have high rates of revascularization or limb loss, respectively 4.
• A systematic evidence review found that adding the ABI to the Framingham Risk Score (FRS) probably has limited value for predicting coronary artery disease (CAD) or cardiovascular disease (CVD) 5.
• An updated evidence report and systematic review found no direct evidence and limited indirect evidence on the benefits of PAD screening with the ABI in unselected or asymptomatic populations 6.

Comparison of Single Level and Multiple Levels ABI

• There is limited evidence comparing the accuracy of single level and multiple levels ABI in detecting PAD.
• A study found that the ABI threshold was not reported, and the superiority of the oscillometric (automated) method for obtaining an ABI reading over the manual method with a doppler probe used by inexperienced operators may be a clinically important finding 2.
• Another study found that poorly compressible arteries were associated with amputation, but not revascularization, while severe disease was associated with revascularization, but not amputation 4.

Clinical Implications

• The ABI is a useful tool for assessing PAD in patients with leg pain on walking that is alleviated by rest.
• The USPSTF recommends that the decision to screen for PAD with the ABI should be made on a case-by-case basis, considering the individual patient's risk factors and medical history 3.
• Further research is needed to determine the optimal method for obtaining ABI readings and to compare the accuracy of single level and multiple levels ABI in detecting PAD.