GLOSARIO PARA INSTRUMENTOS DE DEFENSA

While the focus of this research is the costs and effectiveness of prehospital critical care for OHCA, a few important observations on the costs of in-hospital care and post-discharge resource use should be noted.

For patients with OHCA where resuscitation is unsuccessful and who are declared dead on scene no further costs, other than those described in the previous section, occur. On the other hand, a large proportion (25% in the preliminary ALS cohort) of patients with OHCA survive the prehospital phase of their care and are admitted to a hospital. If active treatment is continued in hospital, patients are admitted to ICU, where the costs of a single day’s care

is about the same as that of a prehospital critical care team attending the patient. On average, I estimated the costs of in-hospital treatment to be approximately £22,000 for patients surviving to hospital discharge and £8,500 for patients who die in hospital. The major contributors to these costs are ICU-bed days (all patients) and interventions such as PPCI, ICD implantation or coronary artery bypass graft surgery (survivors only).

Further costs can accumulate after hospital discharge; most importantly the long-term care services required for the small proportion of patients who survive to hospital discharge with poor neurological function (over £40,000 per year). The magnitude of downstream costs in the OHCA pathway, compared to the prehospital costs alone, emphasise the importance of analysing the complete pathway, which I was able to do through the use of decision analysis modelling as described in Section 6.2. The following paragraphs will now focus on the results of this complete pathway analysis.

6.4.3 Cost-effectiveness of Advanced Life Support for out-of-hospital

cardiac arrest

Utilising data from publications most relevant to the UK population and current EMS systems’ configuration, I was able to estimate the cost-effectiveness of paramedic-delivered ALS for OHCA to be approximately £11,500 per QALY. With the upper limit of the interquartile range at approximately £16,800, this makes ALS for OHCA almost certainly cost-effective at a NICE WTP threshold of £20,000 per QALY (National Institute for Health and Care Excellence, 2013). While a number of previous publications address the cost-effectiveness of individual aspects of prehospital care or hospital care for OHCA (Marti et al., 2017; Moran et al., 2015; Merchant

et al., 2009), very few address the cost-effectiveness of ALS for OHCA in the context of the

complete patient pathway. Naess and Steen (2004) estimated that the cost-effectiveness of ALS for OHCA in Norway was €6,632 (approximately £6,000) per QALY. This much lower estimate is likely due to inflation (since the year of publication was 2004) and recent developments in hospital-based post-cardiac arrest care, with higher rates of intervention and associated higher costs (Nolan et al., 2016; Lai et al., 2015).

More recently, Ginsberg, Kark and Einav (2015) reported the cost-effectiveness of ALS for OHCA to be $28,864 per Disability Adjusted Life Year (DALY) averted, in an Israeli EMS system. The conversion from DALY averted to QALY gained depends on many factors and, in this context, probably ranges between 0.7 to 1.3 (Sassi, 2006). The corresponding value for the cost-effectiveness calculated by Ginsberg, Kark and Einav (2015) is therefore likely to be in

the range of £15,000 - £28,500 per QALY. As neither of these studies were undertaken in the UK setting, transferability of the results is difficult.

Within the limitations of the research presented here, as well as taking previous research findings into account, it is fairly certain that paramedic-delivered ALS is a cost-effective treatment for OHCA in the UK. Furthermore, in terms of £ per QALY, it compares favourably with a range of interventions currently funded by the NHS (Pharoah et al., 2013; Hartwell et

al., 2005).

6.4.4 Investigating cost-effectiveness of prehospital critical care

The purpose of creating this decision analysis model is to assess the cost-effectiveness of prehospital critical care for OHCA. Once the effectiveness data are available in the next chapter, I will input this data to the model and present the results at that stage. In the meantime, running the model with probabilistic sensitivity analysis and various assumptions allowed me to examine the impact of prehospital critical care on downstream costs and to predict a minimally economically important difference in survival rates, which I can use to test the appropriateness of my sample size in the next chapter.

Using the cost-effectiveness acceptability framework in Figure 6.8 (Gray et al., 2011) , I have shown that the minimally economically important difference in survival rates after OHCA depends on the stakeholders’ willingness-to-pay threshold as well as the degree of certainty they consider suitable to make a funding decision. For example, if one wanted to be 90% certain that prehospital critical care is a cost-effective intervention for OHCA, at a willingness- to-pay threshold of £20,000 per QALY, research would need to be powered to detect an absolute improvement in survival rates from approximately 9% to 14%, when compared to ALS care. On the other hand, a 1% absolute difference in survival with prehospital critical care, which could only be ruled out with a very large sample size, has a less than 1% chance of being cost-effective.

In addition to rates of survival to hospital discharge, the cost of prehospital critical care is considerably influenced by the associated rates of survival to hospital arrival, as shown in Table 6.6. For example, an improvement in survival to hospital discharge of 2% might be cost- effective, if the prehospital critical care team achieves this effect without increasing the proportion of patients admitted to hospital. This could be achieved through clinical decisions to switch to palliative treatment in patients with ROSC but also factors such as a poor quality of life or significant co-morbidities which suggest that further treatment is not in the patient’s best interest. However, if the increase in survival to hospital discharge of 2% is due to a higher

rate of ROSC and survival to hospital arrival, as a result of the interventions provided by the prehospital critical care team, the cost-effectiveness is decreased (due to the associated hospital treatment costs), and prehospital critical care is now unlikely to be cost-effective. NICE does not stipulate a fixed threshold for cost-effectiveness, but states that factors other than costs are considered in the decision-making process for funding recommendations (National Institute for Health and Care Excellence, 2013). However, a common interpretation of the NICE guidance is that interventions costing less than £20,000 per QALY should be adopted as cost-effective (Appleby, 2016). For interventions with an incremental cost- effectiveness ratio (ICER) of £20,000 to £30,000 per QALY additional considerations, such as the strength of the evidence, should be considered but cost-effectiveness is unlikely (Appleby, 2016; Claxton et al., 2015). Interventions with an ICER higher than £30,000 per QALY are generally not recommended for implementation in the NHS, with the notable exception of interventions delivered in end-of-life situations and the Cancer Drugs Fund (Leigh and Granby, 2016; Cookson, 2013).

Combining the above variables and information, Table 6.6 would suggest a minimally economically important difference in survival rates after OHCA of 4%, when comparing prehospital critical care to ALS. The research underpinning the clinical effectiveness of prehospital critical care will be of observational design. Therefore, funders would want to be certain that the estimated ICER is well below the threshold of £30,000 per QALY. As can be seen in Table 6.6, an absolute improvement in survival of 4% with prehospital care is the minimal clinical effect at which the 95% confidence intervals for the ICER estimation do not include £30,000 per QALY and the point estimates are below £20,000 per QALY. 4% is therefore the treatment effect of prehospital critical care which the observational research presented in the next chapter should be powered to detect.

6.5 Challenges and limitations

The most important limitation of this economic analysis is the fact that it is largely based on a theoretical construct of the costs and effects of the care pathway for OHCA. As such, certain assumptions about what happens in reality had to be made and must be assumed to reflect reality accurately, in order for the model to be internally valid (Briggs, Claxton and Sculpher, 2006). Nevertheless, any model will always be a simplification of reality.