Accurate and timely diagnosis of peripheral arterial disease (PAD) can be a daunting task, particularly if based only on physical examination, which requires a skilled and experienced examiner. There are far better diagnostic methods, like modern medical devices for measuring Ankle-Brachial Index (ABI). However, the ABI score has value beyond diagnosing PAD.
Cardiovascular diseases (CVDs) in general are quite insidious medical conditions that often exhibit symptoms when they are already difficult to treat and manage or are even in the life-threatening stage (it should therefore come as no surprise that they are the leading cause of mortality worldwide) . However, they need not be associated with extreme mortality rates to have a profound negative impact on the person’s quality of life (heart conditions in general are, for example, negatively associated with mental and emotional well-being) .
One such example is, of course, PAD, which can often be reliably diagnosed (due to the often asymptomatic nature of the disease as up to 40% of patients are entirely asymptomatic and only 10% have typical symptoms) only through modern diagnostic methods, preferably ones that eliminate or at least greatly mitigate the errors on the part of the examiner [3, 4].
The same diagnostic methods, i.e. ABI score measurement (most practical and cost-effective option), are also suitable for other diagnostic purposes that are not directly linked to PAD. Namely, a low or otherwise abnormal ABI score is indicative of possible atherosclerosis in coronary and non-coronary (other than those in the lower extremities) arterial beds . There is also evidence that decreased ABI is associated with greater risk of ischaemic stroke .
The ABI score is an important indicator of overall cardiovascular health and can improve the accuracy of cardiovascular risk prediction beyond the FRS (Framingham Risk Score) .
Additionally, and the topic of this blog post, the ABI score is highly useful for differentiating between various types of leg ulcers and assessing their healing potential, which is (not exclusively) connected to possible PAD or other (vascular) diseases and medical conditions like diabetes mellitus. Yet the ABI is often underutilised in this role, much to the detriment of patients who bear the brunt of both the symptoms and improper (or no) treatment based on misdiagnosis of their condition.
Amongst the various vascular disorders that can affect individuals (to a varying degree) is chronic venous disease (CVD), which is prevalent about equally in both genders (certain conditions are more prevalent in one gender than the other) and in general affects about 83.6% of the global population .
The term CVD actually covers a wide spectrum of venous disorders, from telangiectasias (spider veins), reticular veins and varicose veins, all of which are very common (e.g. about 84% of the population have spider veins), to chronic venous insufficiency (CVI), which is a far more serious condition as it can lead to development of venous ulcers . They are estimated to be prevalent in about 0.3% of the adult population, with some studies indicating that at least 1% of individuals have a history of open or healed ulceration .
However, despite relatively low prevalence of venous leg ulcers in the general (adult) population, they represent the majority (72%) of all cases of leg ulceration, followed by arterial (insufficiency) ulcers (also known as ischaemic ulcers/wounds) that encompass 10% to 30% of all ulcers, while neuropathic leg ulcers that primarily affect diabetic patients have a prevalence rate of between 15% and 25% .
Of those, arterial ulcers (the essential and advanced stage of PAD that if left untreated can progress into gangrene) are particularly difficult and expensive to treat in comparison with venous ulcers, although neuropathic ulcers are not far behind as they are associated with a host of serious complications, including osteomyelitis .
Regarding arterial and venous ulcers: a study of the costs of chronic wound treatment in Medicare (a national health insurance programme in the USA) patients in 2014 revealed that on average the treatment of arterial ulcers cost $9105 per patient, while venous ulcers cost only $1252 (including the treatment of associated infections) .
The economic aspect aside, the main issue with lower-extremity ulcers, from a clinician’s point of view, is differentiating between the different types – a difficult task as there may be cases of ulcers with mixed etiology (a study encompassing 555 patients with 689 leg ulcers revealed that 100 or 14.5% of assessed limbs had ulcers of both arterial and venous origin) .
An ABI measurement can dispel any doubt about the type of ulceration and underlying pathophysiological mechanism. A score of between 0.8 and 1.20 indicates that wounds (if present) are caused by venous insufficiency, while a score of 0.79 or less, down to 0.51, implies mixed (venous/arterial) ulcers (15). A score of 0.5 or less indicates PAD .
The diagnosis (ABI measurement) is usually performed by using a Doppler probe and a sphygmomanometer although there are far more convenient methods for use in specialised settings and for large scale preventive screening of at-risk individuals in general practice .
Any treatment of leg ulcers should therefore be pivoted on a diagnosis based on the ABI and supplemented with an additional test such as venous duplex scanning (better assessment of venous issues) or TBI (Toe-Brachial Index), if the examined patient has incompressible arteries (often those with diabetes and/or renal insufficiency) .
Despite this well researched and supported fact, however, ABI assessment is still greatly underutilised. For example, in the UK alone, a comprehensive study has found that an astounding 40% of patients with leg ulcers had not received an ABI assessment or it was unclear whether a recording had been taken and that around 31% of patients with venous leg ulcers were not receiving compression therapy .
Arterial assessment on the basis of an ABI measurement is useful for purposes beyond diagnosing PAD, including but not limited to differentiating between lower-extremity ulcers of arterial and venous etiology.