Table 1 Model Variables: base case patient probabilities, costs, and utility estimates

Probabilities

 Baseline rate of stroke on aspirin, %/year

4.5

3–6

[23, 24]

 Relative risk of stroke with warfarin compared with aspirin

0.48

0.37–0.63

[23, 24]

 Baseline rate of major hemorrhage (including ICH) on warfarin, %/year

2.5

2–4

[23, 24]

 Relative risk of hemorrhage with aspirin compared with warfarin

0.59

0.50–0.70

[23]

 Fraction of ICH among major hemorrhage events

0.2

NA

[22]

 Fraction of fatal strokes among stroke events on warfarin

0.082

NA

[24]

 Fraction of fatal strokes among stroke events on aspirin

0.179

NA

[24]

 Fraction of fatal events among ICH

0.364

NA

[25]

 Fraction of fatal major hemorrhages (excluding ICH)

0.049

NA

[25]

Costs ($)

 Warfarin annual cost

180

±50 %

[24]

 Aspirin annual cost

10

±50 %

[24]

 Fatal ischemic stroke

12130

±50 %

Assumption, based on [24]

 Average one-time cost of non-fatal stroke on warfarin

9667

±50 %

Calculated based on [24]

 Average monthly cost of non-fatal stroke on warfarin

2652

±50 %

Calculated based on [24]

 Average one-time cost of non-fatal stroke on aspirin

9610

±50 %

Calculated based on [24]

 Average monthly cost of non-fatal stroke on aspirin

2168

±50 %

Calculated based on [24]

 Intracoronary hemorrhage (ICH) one-time cost

31810

±50 %

[24, 26, 27]

 Intracoronary hemorrhage (ICH) monthly costs

4690

±50 %

[24, 26, 27]

 Major hemorrhage (excluding ICH)

3620

±50 %

[24, 26, 27]

Utilities

 Healthy on warfarin

0.987

unchanged

[28, 29]

 Healthy on aspirin

0.998

unchanged

[28, 29]

 Non-fatal stroke on warfarin, weighted average

0.476

±20 %

[24]

 Non-fatal stroke on aspirin, weighted average

0.426

±20 %

[24]

 Non-fatal ICH

0.4

±20 %

Assumption

 Recurrent stroke

0.12

±20 %

[29]