Peripheral arterial disease - Diagnosing peripheral arterial disease

If your GP suspects peripheral arterial disease (PAD), they will carry out a physical examination of your legs.

PAD can cause various symptoms – some of which your GP will be able spot, but you may not – such as:

shiny skin
brittle toenails
hair loss on your legs and feet
the pulse in your leg being very weak or undetectable
leg ulcers

Your GP may also ask about your symptoms and your personal and family medical histories.

The ankle brachial pressure index

The ankle brachial pressure index (ABPI) test is widely used to diagnose PAD, as well as assessing how well you are responding to treatment.

While you rest on your back, your GP or practice nurse will measure the blood pressure in your upper arms and your ankles. These measurements are taken with a Doppler probe, which uses sound waves to determine the blood flow in your arteries.

They then divide the second result (from your ankle) by the first result (from your arm).

If your circulation is healthy, the blood pressure in both parts of your body should be exactly or almost the same, and the result of your ABPI would be one.

However, if you have PAD, the blood pressure in your ankle will be lower due to a reduction in blood supply, so the results of the ABPI would be less than one.

In some cases, ABPI may be carried out after getting you to run on a treadmill or cycle on an exercise bike. This is a good way to see the effect of physical activity on your circulation, although it will usually need to be done in hospital, as most GP surgeries do not have the facilities to perform this test.

Further testing

In most cases, your GP will be able to confirm a diagnosis of PAD by doing a physical examination, asking about your symptoms and checking your ABPI score.

Further testing is usually only required if:

there is uncertainty about the diagnosis – for example, if you have leg pain but your ABPI score is normal
you do not fit the expected profile of somebody with PAD – for example, you are young and have never smoked
the restriction of blood supply in your leg is severe enough that treatment, such as surgery, may be required

Additional hospital-based tests that can be used include:

an ultrasound scan – where sound waves are used to build up a picture of arteries in your leg; this can identify exactly where in your arteries there are blockages or narrowed areas
an angiogram – where a special liquid known as a contrast agent is injected into a vein in your arm; the agent shows up clearly on a computerised tomography (CT) scan or magnetic resonance imaging (MRI) scan and produces a detailed image of your arteries

In some cases, the contrast agent may be injected directly into the arteries of your leg, and X-rays may be used to produce the images.