Table 1 Base case parameter values and distributions
Parameter | Value | Distribution | Source |
|---|---|---|---|
Clinical | |||
 Risk of death following head injury (first month post-injury) | 0.0208 | Triangular (0.01–0.05) | |
 Tranexamic acid treatment effect on death following head injury | 0.70 | Lognormal (95% CI: 0.45–1.08) | CRASH-3 trial data |
 Standardised mortality ratio (first year*) | 2.89 | Normal (95% CI: 2.36–3.54) | [24] |
 Standardised mortality ratio (after first year^) | 1.56 | Normal (95% CI: 1.27–1.91) | [24] |
GOS outcomes | |||
 Good recovery | 208 | Dirichlet (208, 49, 23, 5) | [26] |
 Moderate disability | 49 | Dirichlet (208, 49, 23, 5) | [26] |
 Severe disability | 23 | Dirichlet (208, 49, 23, 5) | [26] |
 Vegetative state | 5 | Dirichlet (208, 49, 23, 5) | [26] |
Utility | |||
 Good recovery | 0.894 | Beta (α = 4331, β = 513.5) | [25] |
 Moderate disability | 0.675 | Beta (α = 2481.5, β = 1194.8) | [25] |
 Severe disability | 0.382 | Beta (α = 662.2, β = 1071.3) | [25] |
 Vegetative state | −0.178 | Normal (95% CI: −0.330, −0.026) | [25] |
 Average utility (weighted average of utility and GOS outcomes) | 0.796 | By component (above) |  |
Treatment-related costs | |||
 Tranexamic acid | £1.50 | N/A | [29] |
 Needle and syringe | £0.12 | N/A | [30] |
 Treatment administration time (minutes) | 5 | Uniform (2–8) | Assumption |
 Paramedic cost (per hour) | £48 | N/A | [28] |
Hospital-related costs | |||
 Cost of neurosurgery | £7780 | N/A | [32] |
 Proportion receiving neurosurgery | 3.45% | Beta (α = 23.83, β = 667.01) | [4] |
 Initial hospital cost | £476 | N/A | [32] |
 Additional hospital cost (per day) | £328 | N/A | [32] |
 Mean length of stay | 4 days | Gamma (k = 32, θ = 0.125) | [31] |
Adverse event costs | |||
 No tranexamic acid | £27.62 | See Additional file 1 for distributions by component. | |
 Tranexamic acid | £28.72 | See Additional file 1 for distributions by component. | |
Monitoring costs—first year | |||
 Good recovery | £303 | Gamma (k = 25, θ = 9.6) × Inflation index* | |
 Moderate disability | £21,633 | Gamma (k = 25, θ = 686.4) × Inflation index* | |
 Severe disability | £42,737 | Gamma (k = 25, θ = 1356) × Inflation index* | |
 Weighted average (weighted by GOS score) | £8,139 | Calculated by component |  |
Monitoring costs—after first year | |||
 Good recovery | £27 | Gamma (k = 25, θ = 0.96) × Inflation index* | [38] |
 Moderate disability | £1784 | Gamma (k = 25, θ = 64) × Inflation index* | [38] |
 Severe disability | £13,934 | Gamma (k = 25, θ = 500) × Inflation index* | [38] |
 Weighted average (weighted by GOS score) | £1695 | Calculated by component |  |