Some of the tests your doctor may rely on to diagnose peripheral artery disease are:

Physical exam :

Your doctor may find signs of PAD during a physical examination, such as a weak or absent pulse below a narrowed area of your artery, whooshing sounds (bruits) over your arteries that can be heard with a stethoscope, evidence of poor wound healing in the area where your blood flow is restricted, and decreased blood pressure in your affected limb.

Ankle-brachial index (ABI):

This is a common test used to diagnose PAD. It compares the blood pressure in your ankle with the blood pressure in your arm.
To get a blood pressure reading, your doctor uses a regular blood pressure cuff and a special ultrasound device to evaluate blood pressure and flow.
You may walk on a treadmill and have readings taken before and immediately after exercising to capture the severity of the narrowed arteries during walking.

Ultrasound:

Special ultrasound imaging techniques, such as Doppler ultrasound, can help your doctor evaluate blood flow through your blood vessels and identify blocked or narrowed arteries.

Angiography:

Using a dye (contrast material) injected into your blood vessels, this test allows your doctor to view blood flow through your arteries as it happens. Your doctor is able to trace the flow of the contrast material using imaging techniques, such as X-ray imaging or procedures called magnetic resonance angiography (MRA) or computerized tomography angiography (CTA).
Catheter angiography is a more invasive procedure that involves guiding a catheter through an artery in your groin to the affected area and injecting the dye that way. Although invasive, this type of angiography allows for simultaneous diagnosis and treatment. After finding the narrowed area of a blood vessel, your doctor can then widen it by inserting and expanding a tiny balloon or by administering medication that improves blood flow.

Blood tests:

A sample of your blood can be used to measure your cholesterol and triglycerides and to check for diabetes.