Below is an instruction from Human. Write a response.
    ### Instruction:
    How to diagnose Peripheral Arterial Disease (P.A.D.) ?
    ### Response:
    There are several tests used to diagnose P.A.D. These include - an ankle-brachial index (ABI). This test compares blood pressure in your ankle to blood pressure in your arm. It shows how well blood is flowing in your limbs.  - a Doppler ultrasound. This test uses sound waves to show whether a blood vessel is blocked.
    