Table 5.

Tools Used to Measure Outcomes in PAD, and Examples of Trial Designs That Could Use These as Primary or Secondary Outcomes

Outcome Category	Tool	Outcome Variable	Potential Trial
Function/observer measures	Graded exercise treadmill	Time(peak walk time and claudication onset time)	Trials in claudication using drugs,^26,29 revascularization, cell-based therapies, or exercise^24,30^*
	6-min walk	Meters	Trials in claudication using drugs, revascularization, cell-based therapies, or exercise,¹⁹ especially in frail populations
	4-m walk	Meters per second	Trials in claudication using drugs, revascularization, cell-based therapies, or exercise, especially in frail populations
Function/subject perception	Quality of life(by domains or total score)	Unit score	Trials in claudication or critical limb ischemia using drugs,^29,75 revascularization,⁴⁹ cell-based therapies, or exercise^20,30
Clinical	Death/myocardial infarction/stroke	Absolute incidence and hazard ratio (vs comparison treatment using survival analysis)	Trials in claudication (safety) or critical limb ischemia using drugs,²⁶ revascularization,^{31,38,41,49,50} cell-based therapies, or exercise
	Clinically driven repeat revascularization^†(target lesion/ vessel revascularization)	Absolute incidence and hazard ratio (vs comparison group using survival analysis)	Trials in claudication or critical limb ischemia using revascularization (percutaneous or open surgery)
	Major amputation^†	Absolute incidence and hazard ratio (vs comparison group using survival analysis)	Trials in claudication (safety) or critical limb ischemia using drugs, revascularization,^{31,38,41,49,50} cell-based therapies, or exercise
Anatomic	Restenosis/graft occlusion	Angiography: percent stenosis vs reference segment	Mechanistic end point in trials in claudication or critical limb ischemia using drugs⁸⁶ or revascularization (percutaneous^38,41,49,50 or open surgery)³¹
		Duplex ultrasound: percent stenosis based on ratio of PSV in lesion to PSV in proximal reference segment

PAD indicates peripheral artery disease; and PSV, peak systolic velocity. It is unclear what angiographic restenosis or PSV ratio reflects a clinically important measure f restenosis. References are examples of studies using these outcomes.

Treadmill tests may be biased by a learning effect if the intervention is treadmill-based exercise and offered only to 1 treatment group.

^†

Revascularization defined by clinical or functional criteria (not imaging) and major amputation determined by prospective criteria.