Table 3.

Tests of effect modification by health system complexity and chronic obstructive pulmonary disease–volume

Variable	HR (95% CI)	Interaction P Value
Model 1
CAN score	1.02 (1.01–1.03)
Site complexity	1.38 (0.88–2.16)
CAN × site complexity	0.997 (0.99–1.01)	0.45
Model 2
CAN score	1.02 (1.01–1.02)
Site COPD-volume	1.38 (0.85–2.24)
CAN × site COPD-volume	0.997 (0.99–1.00)	0.24

Definition of abbreviations: CAN = care assessment needs score; CI = confidence interval; COPD = chronic obstructive pulmonary disease; HR = hazard ratio.

Values are presented as HR with 95% CIs. Each model is adjusted for age and clustered by site.