Choosing between a manual or automated ankle-brachial index (ABI) test

Historically, ankle-brachial index (ABI) testing was always done manually, and still is at some sites. Now, automated ABI machines are available in many locations, and they have their benefits. Let’s cover a few differences between manual and automated ABIs so you can pick between the two and appreciate their advantages.

Manual ABIs have three main advantages:

• They are not hard to learn.
• They are reliable.
• They only need a blood pressure cuff with a pump and a Doppler pen.

Manual ABI tests are a great option when a machine isn’t available. But, a downside to a manual ABI is that you cannot print out a report to share.

In fact, ABI ratios can be even be calculated without the use of a Doppler pen. In an emergency situation when an ABI machine or a Doppler pen is not available, you can simply grab a portable blood pressure (BP) machine. Put the cuff on each limb and take the patient’s systolic pressures to manually calculate the ABI ratios.

This is less accurate because without the Doppler you will not hear the waveforms. Doppler waveforms are more sensitive and are typically faster at detecting the earliest pulse. However, blood pressure cuffs can give you a general idea if a disease is present—especially if you see a big drop between the arm and ankle, which is helpful in an emergency.

If a manual ABI is performed, there is still the option of using an older photoplethysmography (PPG) portable recorder to perform digit PPG and toe-brachial index (TBI) testing. The results can be printed and scanned into the patient’s chart.

Of course, when one is available, an automated ABI machine has several advantages:

• Automated protocols
• Automated calculations
• Ease of TBI testing
• Ability to print / transfer a report with analog waveforms

As you can see, an automated ABI machine may be preferable, but a manual ABI still provides information that is reliable and useful for diagnostic purposes.