Post-exercise criteria to diagnose lower extremity peripheral artery disease: Which one should I use in my practice?

We read with great interest the paper from Aday et al. entitled ‘Comparison of different exercise ankle pressure indices in the diagnosis of peripheral artery disease’. ¹ In their paper, the authors found that a post-exercise ankle–brachial index (ABI) < 0.90 exhibited the best sensitivity as compared with a post-exercise ABI decrease > 20% and a post-exercise ankle pressure decrease > 30 mmHg. This paper is important given the sparse literature and lack of standardization about how to perform post-exercise ABI.^2–5 Before using post-exercise criteria to detect lower extremity peripheral artery disease (PAD) in clinical practice, vascular physicians should pay attention to several points that were not addressed in this paper:

In our opinion, it is desirable to measure the symptomatic leg first in order to measure the ankle pressure as quickly as possible after the end of exercise. ⁶ According to published guidelines for measuring the ABI at rest, we use the same artery for measurement of the post-exercise ABI as was used for the resting ABI.^5,7 It is also suggested to mark the skin area where the pressure is recorded at rest in order to reduce the time between the end of exercise and the first post-exercise measurement. Exercise characteristics and time of measurement after exercise have to be considered for the exercise ABI test. In previously published studies, the post-exercise ABI decrease > 20% was validated on a treadmill at 1.5 mph (2.4 km/h) and 7% grade with a pressure measurement performed 2 minutes after the end of exercise, while the post-exercise ankle pressure decrease > 30 mmHg was validated on a treadmill at 2.5 mph (4 km/h) and 10% grade for 1 minute with a pressure measurement performed 30 seconds after the end of exercise.^2,3 According to Aday and colleagues, the post-exercise < 0.90 criterion can be used to assess for suspected PAD among patients with an ABI at rest ⩾ 0.90 with a treadmill test (10% grade and 1.5 mph) and a post-exercise pressure measurement performed 2 minutes after the end of exercise. ¹ However, using this exercise criterion (< 0.90), the area under the curve (AUC) for 75% stenoses among individuals with normal resting ABIs is low (0.5209). Do the authors think that a greater treadmill grade or a greater treadmill speed or a shorter time after exercise to measure the pressure would improve the AUC?