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Table 1 Key model assumptions and parameters

From: Costs and expected gain in lifetime health from intensive care versus general ward care of 30,712 individual patients: a distribution-weighted cost-effectiveness analysis

Key model assumptions Description Sources
Patients General adult ICU population (n = 40,916), Norway 2008–2010. One or more organ failures, case mix, >90% of annual ICU admissions in the country Norwegian Intensive Care Registry
Intervention ICU admission  
Comparator Hypothetical ICU refusal and general ward treatment of the same patients  
Setting 38 mixed medical-surgical ICUs out of a total of 42 ICUs in publicly funded hospitals operated by local health trusts under four state-owned regional health authorities.  
Health outcome Quality-adjusted life years (QALYs)  
Resource use Hospital costs were summed in Norwegian kroner (NOK), converted to NOK in 2016 using the CPI and to Euro (€) using OECD PPP: 1 USD = 9.4 NOK = 0.75 Euros Statistics Norway, [51]
Severity of disease Expected lifetime health if rejected to the ICU. Measured as number of lifetime QALYs. [13]
Distribution weights Higher weights assigned to health gains to patients with more severe conditions; results in more favourable cost-effectiveness estimates. Additional file 2, [13, 62]
Perspective Hospital, health care provider [50]
Time horizon Lifetime [50]
Discounting 4% annually of health benefits and incremental health care costs post-hospital discharge. [50]
Heterogeneity Analysis of total study population, subgroups by type of admission and individual admissions.  
General cost-effectiveness threshold range 275,000–800,000 NOK per QALY ≈22,000–64,000 PPP-adjusted € per QALY. [56, 57]
Model parameter Parameter values Sources
. Base case Range Distribution .
Age Individual age Individual age Observed ICU cohort 2008–2010
Transition probabilities:     
 Effect of ICU admission on hospital mortality     
 Predicted hospital mortality if ICU patient Individual SAPS II, calibrated model   Observed ICU cohort 2008–2010, [35]
 Predicted hospital mortality if general ward Individual SAPS II, modified model (β1 = 0.09) β1 = 0.0737 to 0.14 Scaled betaa Fig. 1, Additional files 1 and 2
 Annual mortality after hospital discharge Age-specific *3–1 over 3 years *1 to *5–1 over 10 years Uniform Life table Norway 2011, [34], Additional file 2
Length of hospital stay, mean (median) days     
 If ICU, weighted sum of     
  Died ICU LOS ICU 4.8 (1.7) 0.6–5.0 (IQR) Observed ICU cohort 2008–2010
  LOS ward post ICU 0 NA NA  
  Died ward LOS ICU 5.4 (2.6) 1.3–5.9 (IQR) Observed ICU cohort 2008–2010
  LOS ward post ICU 2.5 NA Gamma (scale = 0.5, shape = 5)  
  Survived hospital LOS ICU 4.1 (2.0) 1.1–4.1 (IQR) Observed ICU cohort 2008–2010
  LOS ward post ICU 10 NA Gamma (scale = 2, shape = 5)  
 If general ward, weighted sum of     
  Died hospital LOS ward LOS if ICU and dead *0.9 NA Gamma  
  Survived hospital LOS ward LOS if ICU and hospital survivor *1.1 NA Gamma  
Cost units     
 Cost of ICU bed-day €3980 €2390 to €5570 Scaled betab Additional file 2, [18]
 Cost of general ward bed-day €640 €320 to €950 Scaled betab Additional file 2
 Annual health care cost survivors, year 1 €6400 €80 to €12,700 Scaled betab [47, 48]
  Years 2–5 Year 1 *0.6, *0.5, *0.4, *0.3    
Health-related quality of life weights *0.8 *0.6 to 0.9 Scaled betac Additional files 1 and 2, [19, 38,39,40,41,42]
 Age-matched reference value reduced 20% for 5 years after discharge, equally for both treatment options 18–19: 0.90 0.72 0.54 to 0.81   
20–29: 0.89 0.71 0.53 to 0.80   
30–39: 0.88 0.70 0.53 to 0.79   
40–49: 0.86 0.69 0.52 to 0.77   
50–59: 0.84 0.67 0.50 to 0.76   
60–69: 0.81 0.65 0.49 to 0.73   
70–79: 0.79 0.63 0.47 to 0.71   
80+: 0.73 0.59 0.44 to 0.66   
Distribution weights based on lifetime QALYs Linear NA NA Additional file 2, [13, 62]
  1. Scaled beta: min + (max – min) × beta(alpha,beta)
  2. abeta(alpha = 2,beta = 3.5)
  3. bbeta(alpha = 2,beta = 2)
  4. cbeta(alpha = 4,beta = 2
  5. CPI consumer price index, ICU intensive care unit, IQR interquartile range, LOS length of stay, NA not applicable, NOK Norwegian kroner, PPP purchasing power parity, SAPS Simplified Acute Physiology Score, USD United States dollar