Table 1 Key model assumptions and parameters
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. | ||||
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. | ||||
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 | ||
Annual mortality after hospital discharge | Age-specific *3–1 over 3 years | *1 to *5–1 over 10 years | Uniform | ||
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 | ||
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 | ||
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 | ||
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 | ||