Healthcare-associated Primary blood-stream infections (P-BSI)
Risk of symptomatic infection and duration of disease
A healthcare-associated primary bloodstream infection (HA primary BSI) in adults was defined in accordance with the ECDC case definition (ECDC, 2012).
The distribution into complicated vs. uncomplicated cases resulting from an initial symptomatic infection was 34–47% vs. 53–66% (Engel, 2007; Pittet, 1995; Rangel-Frausto, 1995).
The disability weights for hospitalisation in an intensive care unit (ICU) and for complicated sepsis already included the disease weight for short-term complications. Therefore, details of the risk differences are only provided for information purposes since they are not required for the outcome tree. Short-term complications include renal failure with renal replacement therapy (17–23%) (Gallagher, 2014; Oppert, 2008; Wisplinghoff, 2004), critical illness myopathy/polyneuropathy (50–75%) (Khan, 2006; Garnacho-Montero, 2001) and sepsis-associated encephalopathy (50–62%) (Eidelman, 1996).
For some of the long-term complications, we did not identify any relevant literature for cases with a health status of sepsis or BSI, although information was found for Acute Respiratory Distress Syndrome (ARDS). As ARDS frequently occurs following severe sepsis, we agreed with the clinical experts that ARDS could be used as a proxy for complicated sepsis.
Mortality was set to 9.4–20.3% (Renaud, 2001; Olaechea, 2013) and length of hospital stay) to 10–13 days (Renaud, 2001; Olaechea, 2013).
Risk of complications
Post-traumatic stress disorder (PTSD) is a significant sequelae of severe sepsis/septic shock. Given a population prevalence of 7.8% (Kessler, 1995), the resulting risk of developing PTSD was set at 13–21% (Deja, 2006; Schelling, 1998; Stoll, 1999; Kapfhammer, 2004; Hopkins, 2005).
Two studies were identified that reported on the risk of developing cognitive impairment following BSI, but the reported values differed significantly: 11% for Iwashyna et al. (2010) and 47% for Hopkins et al. (2005) . Major methodological differences included different ascertainment methods and study participants’ health states at the inclusion phase.
A certain degree of physical impairment was reported in all patients during follow-up after severe sepsis/septic shock (Hopkins, 2005; Herridge, 2003; Hofhuis, 2008).
We assumed that the risk of chronic/long-term renal replacement therapy (RRT) was the same for all instances of acute renal failure, irrespective of cause. A total of 8% of BSI patients needed RRT at the onset of BSI (Wisplinghoff, 2004). In accordance with the American College of Chest Physicians/Society of Critical Care Medicine (ACCP/SCCM) definition, we classified BSI patients with acute renal failure as “complicated sepsis”. Thus, the percentage of BSI patients needing RRT (8%) was weighted with severity proportions (complicated sepsis in 33.7–47.1%) and a range of 16.6–23.2% was estimated for patients with complicated sepsis that require RRT at the onset of BSI. In conclusion, 16.6–23.2% of all patients with complicated sepsis patients were estimated to require RRT in the short-term and of those 5.4% were estimated to require long-term maintenance RRT. Assuming a background risk of zero, the risk of requiring long-term RRT after severe sepsis was 0.9–1.3%.
Model input summary
Table 1. Transition probabilities used in the outcome tree
Health outcome |
Distribution of health states in health outcome |
Transition probability |
Source/assumption |
Symptomatic infection Uncomplicated Complicated |
53-66% 34-47% |
|
Engel, 2007; Pittet, 1995; Rangel-Frausto, 1995 |
Fatal cases following symptomatic infection |
|
9.4-20.3% |
Renaud, 2001; Olaechea, 2013 |
Post-traumatic stress disorder (PTSD) following severe sepsis or septic shock |
|
13-21% |
Kessler, 1995; Deja, 2006; Schelling, 1998; Stoll, 1999; Kapfhammer, 2004; Hopkins, 2005 |
Cognitive impairment following severe sepsis or septic shock |
|
11-47% |
Hopkins, 2005; Iwashyna, 2010 |
Physical impairment following severe sepsis or septic shock |
|
100% |
Hopkins, 2005; Herridge, 2003; Hofhuis, 2008 |
Renal failure and renal replacement therapy following severe sepsis or septic shock |
|
0.9-1.3% |
Gallagher, 2014; Wisplinghoff, 2004 |
Table 2. Disability weights and duration
Health
outcome |
Disability Weight (DW) (Haagsma, 2015) |
Duration |
||
DW |
Label |
In years |
Source/assumption |
|
Symptomatic infection Uncomplicated
Complicated |
0.125 (0.104-0.152)
0.655 (0.579-0.727) |
Infectious disease, acute episode, severe Intensive care unit admission |
0.027-0.036 |
Renaud, 2001; Olaechea, 2013 |
Post-traumatic stress disorder (PTSD) following severe sepsis or septic shock |
0.088 (0.07-0.108) |
Subacute sclerosing panencephalitis – phase 1 (chosen according to best fitting description) |
Remaining life expectancy |
|
Cognitive impairment following severe sepsis or septic shock |
0.043 (0.026-0.064) |
Intellectual disability, mild |
Remaining life expectancy |
|
Physical impairment following severe sepsis or septic shock |
0.011-0.053 |
Range between Motor impairment, mild and Motor impairment, moderate |
Remaining life expectancy |
|
Renal failure and renal replacement therapy following severe sepsis or septic shock |
0.030-0.487 |
Range between End-stage renal disease, on dialysis and End-stage renal disease, with kidney transplant |
Remaining life expectancy |
|
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