Table 3. Interaction effect on the association of institutional volume with restenosis risk.

		Odds ratio of higher-versus lower-volume centers for 12-month restenosis	P for interaction
Overall		0.46 [0.23 to 0.94]
Age	< 75 years	0.59 [0.25 to 1.37]	0.33
	≥ 75 years	0.33 [0.11 to 1.00]
Sex	Female	0.66 [0.15 to 2.81]	0.62
	Male	0.44 [0.20 to 0.95]
Body mass index	< 22 kg/m2	0.41 [0.15 to 1.15]	0.90
	≥ 22 kg/m2	0.50 [0.20 to 1.27]
Current smoking	No	0.38 [0.14 to 1.02]	0.44
	Yes	0.61 [0.26 to 1.47]
Hypertension	No	0.77 [0.10 to 5.66]	0.58
	Yes	0.45 [0.21 to 0.94]
Dyslipidemia	No	0.46 [0.12 to 1.72]	1.00
	Yes	0.45 [0.19 to 1.04]
Diabetes mellitus	No	0.51 [0.20 to 1.29]	0.84
	Yes	0.43 [0.16 to 1.16]
Regular dialysis	No	0.44 [0.19 to 1.00]	0.96
	Yes	0.37 [0.08 to 1.87]
Myocardial infarction	No	0.45 [0.20 to 0.99]	0.70
	Yes	0.59 [0.15 to 2.31]
Aspirin use	No	0.69 [0.19 to 2.48]	0.49
	Yes	0.41 [0.18 to 0.90]
Thienopyridine use	No	0.62 [0.25 to 1.54]	0.26
	Yes	0.28 [0.09 to 0.87]
Dual antiplatelet therapy	No	0.62 [0.27 to 1.42]	0.19
	Yes	0.24 [0.07 to 0.86]
Anticoagulant use	No	0.46 [0.22 to 0.98]	0.95
	Yes	0.44 [0.07 to 3.01]
Cilostazol use	No	0.35 [0.14 to 0.83]	0.16
	Yes	0.83 [0.29 to 2.37]
Statin use	No	0.39 [0.16 to 0.97]	0.60
	Yes	0.57 [0.21 to 1.54]
Rutherford classification	category 2/3	0.43 [0.21 to 0.92]	0.53
	category 4	0.85 [0.11 to 6.38]
TASC II classification	class A to C	0.45 [0.21 to 0.98]	0.86
	class D	0.50 [0.14 to 1.74]
Chronic total occlusion	No	0.56 [0.26 to 1.17]	0.55
	Yes	0.36 [0.09 to 1.42]
Total stent length	< 100 mm	0.49 [0.22 to 1.11]	0.84
	≥ 100 mm	0.40 [0.13 to 1.26]
Mean stent diameter	< 9.0 mm	0.68 [0.26 to 1.78]	0.37
	≥ 9.0 mm	0.36 [0.13 to 1.00]
Femoropopliteal lesion	No	0.43 [0.13 to 1.36]	0.81
	Yes	0.46 [0.20 to 1.10]
Contralateral iliac revascularization	No	0.44 [0.17 to 1.11]	0.98
	Yes	0.41 [0.15 to 1.14]
Stent use	single	0.45 [0.21 to 0.96]	0.79
	multiple	0.53 [0.15 to 1.90]
Intravascular ultrasound use	No	0.55 [0.20 to 1.54]	0.66
	Yes	0.42 [0.14 to 1.29]
Hemostasis device use	No	0.41 [0.15 to 1.16]	0.62
	Yes	0.57 [0.24 to 1.37]
Pre-ballooning	No	0.49 [0.17 to 1.43]	0.93
	Yes	0.44 [0.18 to 1.08]
Procedure time ≤ 1 hour	No	0.53 [0.17 to 1.64]	0.97
	Yes	0.52 [0.22 to 1.25]
Contrast agent	< 100 ml	0.48 [0.19 to 1.21]	0.94
	≥ 100 ml	0.42 [0.15 to 1.12]
Radiation time	< 30 min	0.68 [0.31 to 1.50]	0.28
	≥ 30 min	0.32 [0.09 to 1.11]