Is it possible to measure Ankle-Brachial Index (ABI) on patients with wounds?

Regardless of their aetiology, chronic wounds are a growing medical and socioeconomic problem, affecting individuals in developed and developing countries alike. There are several reasons for this: some of them overlap, but they are primarily associated with the rising prevalence of diabetes mellitus, obesity and physical inactivity, and vascular diseases. Of the latter, none is as serious as peripheral arterial disease (PAD), both as a cause of chronic wounds and a negative factor to the effective treatment and management of wounds of different aetiology.

In this blog you will learn:

• What are chronic wounds?
• How prevalent and costly are chronic wounds?
• How to use Ankle-Brachial Index (ABI) in wound care?

What are chronic wounds?

The exact definition of a chronic wound varies between various national and international medical organisations, but it is generally described as a wound that does not heal in a predictable length of time. Just what is regarded as a predictable length of time is the root of the problem in defining what precisely a chronic wound is [1]. The published time intervals range anywhere from four weeks to three months, causing confusion amongst clinicians and delaying proper treatment, diminishing its efficiency, and increasing the likelihood of complications and adverse outcomes [1, 2].

Regardless of their exact definition, the aetiology of chronic wounds is well researched as are their causes and the complexities in their treatment. A comprehensive overview of several large-scale epidemiological studies found that venous ulcers represent the majority (72%) of all cases, followed by arterial insufficiency ulcers (ischaemic ulcers) with prevalence between 10% and 30% and neuropathic ulcers in third place (comprising 15% to 25% of all diagnosed cases) [3]. The list of chronic wounds also includes lymphatic and infectious ulcers, but they constitute a tiny minority of all wounds [3]. A careful reader would note that the prevalence number of first three most common types do not add up — they can occur concurrently, delaying diagnosis and treatment and biasing accurate prevalence estimates.

How prevalent and costly are chronic wounds?

The prevalence of chronic wounds is intimately connected with the underlying causative mechanism connected to known risk factors, including tobacco smoking, diabetes mellitus, and PAD, at the confluence of the first two. Accurate estimates have so far proved vague, but a comprehensive systematic review of prevalence studies of lower-limb ulceration reported prevalence rates from 0.12% to 1.1% of the population and rates of open and healed ulcers of up to 1.8% [4].

Stratification across different countries varies greatly. A study conducted in Ireland in 389 patients found an overall prevalence of 0.12% but it raised to 1.03 % in patient older than 70 years old [5]. A study encompassing the Swedish population, put the prevalence of open ulcers at 0.63% and the overall prevalence of ulcer history at around 2% [6]. On the other side of the world, in India, prevalence estimates for chronic wounds hover around 0.45%, although that number was derived from a single study and is in practice, likely quite higher [7].

Similarly, incomplete data can be found regarding the United States. There were at least 8.2 million patients with chronic wounds in 2018, up from 6.5 million in 2009, but those numbers include only national health insurance program (Medicare) beneficiaries, excluding those insured by other health insurance companies or with no medical insurance [8]. Costs associated with their treatment are likewise unknown but just Medicare spent between $28.1 billion and $31.7 billion in 2014 alone [8]. The most expensive was the treatment of arterial ulcers at $9105, far more than that of venous ulcers (up to $1252) [8]. That should come as no surprise since their treatment regimens are vastly different and may be mutually exclusive in those with an advanced form of the disease (particularly PAD).

How to use Ankle-Brachial Index (ABI) in wound care?

Differentiating between the two types can be difficult without proper diagnostic tools that can help clinicians identify the underlying cause. There are several modern methods available, but none as cost-effective and convenient as the ABI (Ankle-Brachial Index) assessment. Namely, arterial wounds are caused by PAD, which by itself is a largely asymptomatic disease and can only be reliably diagnosed with an ABI assessment [9-13].

The ABI, a ratio between the blood pressure at the ankle and arm, is markedly different in those with healthy arteries but with venous issues, and those with PAD, making it an excellent indicator of ulcer’s aetiology. There are also in-between values in those with both types of ulcers that require a comprehensive, balanced approach to treatment [14]. The answer to the question “Is it possible to measure the ABI on patients with wounds?” is, therefore, a resounding YES and the reason why it was/is used in numerous epidemiological (and other) studies of lower extremity ulceration. They likewise include a study conducted in India that wanted to evaluate the association between abnormal ABI and clinical outcomes in patients with lower limb ulcers and the differences between prevalence rates in India and worldwide [15].

They found that 84% of examined ulcers were of vascular origin and that 52% of them were arterial ulcers — in contrast to the estimated worldwide prevalence of between 10% and 30% [15]. Additionally, researchers noted that the majority of those patients were males with a history of smoking, which is not surprising given its role as the single most prominent modifiable risk factor for PAD, adding further credibility to the recommended preventive screening for PAD, with special emphasis on patients in risk groups [16-20].

Use of ABI measurement in chronic wound assessment should be a prerequisite step before deciding on the proper treatment regimen, particularly in cases of ulcers with mixed aetiology.

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