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Table 1 Inputs of the decision model for the evaluation of IVIG for severe sepsis/septic shock: parameter values and uncertainty over parameter values

From: Intravenous immunoglobulin for severe sepsis and septic shock: clinical effectiveness, cost-effectiveness and value of a further randomised controlled trial

Parameter Source Base case Notes on scenario analyses undertaken Notes on subgroup analyses
Cohort characteristics     
Mean age of a severe sepsis patient at admission to hospital CMPD 63 years old Same as base case Assumed to vary in subgroups defined using age. Sourced from ICNARC database
Proportion of males in a severe sepsis population at admission to hospital CMPD 0.53 Same as base case Assumed to vary in subgroups defined using gender. Sourced from CMPD
Short-term outcomes (ST)     
Probability of dying in hospital when SC is used in the treatment of severe sepsis (baseline risk) CMPD 40.6%, 95% CI (40%, 41.2%) Same as base case Assumed to vary per subgroup (all). Sourced from CMPD
Odds ratio, when IVIG is used to complement SC in the treatment of severe sepsis (based on Model M1) Evidence synthesis (‘Clinical effectiveness of IVIG’) 0.75 , 95% CI (0.58, 0.96) Alternative models tested; see Table 2 Same as base case
Longer-term outcomes (LT)     
Age specific probability of dying in yearly intervals, conditional on patients having survived up to the start of the year. Cuthbertson database and general population life tables 2010 Figure 4. Varies with time. (1) time horizon Assumed to vary for subgroups defined using age and APACHE II score. Sourced from CMPD
(2) time points at which patients reverted to survival of general population
Cost-related parameters     
Costs of overall IVIG therapy Non-stochastic, BNF £5,539.05 Same as base case Same as base case
Costs of SC, when only SC is used in the treatment of severe sepsis Non-stochastic, £0 Same as base case Same as base case
LOS in ICU for patients remaining alive until discharge from hospital CMPD 8.48 (SE = 0.086) Same as base case Assumed to vary for all subgroups. Sourced from CMPD
LOS in ICU for patients dying in hospital CMPD 7.40 (SE = 0.108) Same as base case Assumed to vary for all subgroups. Sourced from CMPD
Costs associated to a day in ICU for a patient with severe sepsis Non-stochastic, reference costs [24] £1,393 Same as base case Same as base case
Overall hospital LOS for patients remaining alive until discharge from hospital CMPD 21.29 (SE = 0.292) Same as base case Assumed to vary for all subgroups. Sourced from CMPD
Overall hospital LOS for patients dying in hospital CMPD 39.07 (SE = 0.325) Same as base case Assumed to vary for all subgroups. Sourced from CMPD
Costs associated to a day in wards other than ICU for a patient with a severe sepsis episode Non-stochastic, reference costs [24] £196 Same as base case Same as base case
Costs incurred between year t-1 and year t after hospital discharge Manns [25] t = 1: £13,654 and t >1: £4,466.5/year (1) ± 50% of Manns’ estimates Same as base case
(2) average annual per capital NHS cost for the general population
Utilities     
In-hospital HRQoL weight associated to severe sepsis patients Drabinsky [26] 0.53 Same as base case Same as base case
HRQoL weight associated to severe sepsis patients at year t Cuthbertson database, Drabinsky [26] t = 1: 0.62 and t >1: 0.6833 Same as base case Same as base case
  1. See NIHR HTA full technical report [10] for a comprehensive reporting of parameter values used to inform the decision model, including those used in subgroup analyses. IVIG, intravenous immunoglobulin; CMPD, Case Mix Programme Database; ICNARC, Intensive Care National Audit & Research Centre; CI, confidence interval; BNF, British National Formulary; SC, standard care; APACHE II, Acute Physiology and Chronic Health Evaluation II; LOS, length of stay; HRQoL, health-related quality of life.