Table 3 Results of one way sensitivity analyses

Scenario*	Outcomes	TP	TS	TFS
Complete case (n = 360)	Cost	2848	2786	3800
	QALY	0.7016	0.7160	0.7301
	Adjusted QALY	0	0.00312	0.01665
	Exacerbation	1.52	1.60	1.24
	Cost/exacerbation avoided	Reference	865	3332
	Cost/QALY		Dominant	57 142
Non-COPD related	Costs	3846	3528	5004
Hospitalisations included	Cost/exacerbation avoided	Reference	2958	5463
	Cost/QALY		342 484	96 271
Zero exacerbations after death	Exacerbation	1.52	1.64	1.28
	Cost/exacerbation avoided	Reference	Dominated	4123
One exacerbation for each period after death†	Exacerbation	1.65	1.84	1.64
	Cost/exacerbation avoided	Reference	Dominated	47 768
Severe COPD (FEV₁ ⩽50% predicted)‡	Cost	2790	2711	4121
	QALY	0.6924	0.6866	0.7021
	Adjusted QALY	0	−0.0031	0.0096
	Exacerbation	1.82	1.82	1.51
	Cost/exacerbation avoided	Reference	Dominant	4293
	Cost/QALY		25 483	141 979
Moderate COPD (50% <FEV₁ <65% predicted)‡	Cost	1402	2341	2701
	QALY	0.7241	0.7567	0.7600
	Adjusted QALY	0	0.0032	0.0096
	Exacerbation	1.01	1.34	0.94
	Cost/exacerbation avoided	Reference	Dominated	18 591
	Cost/QALY		289 509	139 218
Disutility during exacerbation	QALY	0.7031	0.7064	0.7207
	Adjusted QALY	0	−0.0094	0.0073
	Cost/QALY	Reference	Dominated	139 459

*For each scenario, only the outcome(s) that might be affected by the new assumption are reported.
†The ICER in this scenario could be interpreted as cost per one exacerbation free period (28 days) achieved.
‡According to the GOLD criteria:4 severe COPD was defined as observed over predicted FEV₁ of more, less than or equal to 50% of predicted.
COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in 1 s; ICER, incremental cost effectiveness ratio; TP, tiotropium+placebo; TS, tiotropium+salmeterol; TFS, tiotropium+fluticasone/salmeterol; QALY, quality adjusted life years.