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Table 1 Base case parameter values and distributions

From: A cost-effectiveness and value of information analysis to inform future research of tranexamic acid for older adults experiencing mild traumatic brain injury

Parameter Value Distribution Source
Clinical
 Risk of death following head injury (first month post-injury) 0.0208 Triangular (0.01–0.05) [21,22,23]
 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. [3, 32]
 Tranexamic acid £28.72 See Additional file 1 for distributions by component. [3, 32]
Monitoring costs—first year
 Good recovery £303 Gamma (k = 25, θ = 9.6) × Inflation index* [37, 38]
 Moderate disability £21,633 Gamma (k = 25, θ = 686.4) × Inflation index* [37, 38]
 Severe disability £42,737 Gamma (k = 25, θ = 1356) × Inflation index* [37, 38]
 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  
  1. *Costs are presented in 2019/2020 values. Inflator for first year post discharge costs (2006/2007 to 2019/2020) is 1.261, for post-discharge costs beyond the first year (2011/2012 to 2019/2020) is 1.115, and for costs sourced from NHS reference costs (2017/18 to 2019/20) is 1.046