Following a decision to include coverage of economic aspects of interventions in a Cochrane review, the first stage of research is to formulate one or more questions, or objectives, that the economics component of the review will seek to address. Each economics question or objective will determine methodological decisions in subsequent stages of the critical review of health economics studies.
Formulating an economic question requires close consideration of the role and relevance of economic issues to the specific overall review topic. The preliminary questions below are intended to provide useful starting points to help authors and editors conceptualize the role and relevance of economic issues.
What is the economic burden to society (e.g. health system, health or social care providers, individuals, families, employers) of the condition or illness that the intervention is seeking to affect?
What types of incremental resource inputs are required to implement and sustain the intervention, versus comparators (e.g. staff, equipment, drugs, inpatient hospital care)?
What are the incremental resource consequences of implementing the intervention, versus comparators? or How might the intervention impact on the subsequent (downstream) use of resources, versus comparators (e.g. complications, secondary procedures, outpatient visits, time-off-work)?
What are the incremental costs associated with changes in resource use that may result from the intervention, versus comparators (e.g. direct and indirect medical costs, patient out-of-pocket expenses, income from employment)?
What is the economic value associated with incremental beneficial or adverse effects (outcomes) that may result from the intervention, versus comparators (e.g. measures of willingness-to-pay, or utility)?
What are the potential trade-offs between costs (resource use) and beneficial or adverse effects that may need to be considered in a decision to adopt or reject a given course of action?
In considering these preliminary questions, it is important to take the following key issues into account:
Magnitude: What is the likely order of magnitude of different items of incremental resource use or incremental costs associated with the intervention, versus comparators? In other words, which items of resource use (resource inputs and resource consequences) and which costs are likely to be the most important when making choices between alternative interventions?
Time horizon: What is the time horizon over which important costs (resource use) and effects (outcomes) are likely to accrue? Cochrane reviews implicitly establish a time horizon for effects by specifying intermediate and final endpoint measures of effects as target outcome measures. There is a parallel need to consider whether the same time horizon is applicable when all relevant costs (resource use) and effects are considered together.
Analytic viewpoint: Who is likely to bear the incremental costs associated with an intervention, versus comparators, and who receives the incremental benefits (e.g. patient, patient’s family, healthcare provider or third-party payer, healthcare system, society)? Some costs (resource use) are relevant from one analytic viewpoint, but not from another. For example, the cost of providing informal care may be relevant from a patient or a societal viewpoint, but may be excluded when a narrower perspective is selected, such as that of the healthcare system. A further complication is that some resource use or cost categories may overlap between perspectives. Given the range of end-users of Cochrane reviews, a pragmatic approach is to consider the full range of perspectives and then to report not only measures of resource use and cost, but also who bears the cost or incurs the resource use.
Clinical event pathways can provide a further useful tool to help conceptualize the role and relevance of economic issues to a specific review topic. A clinical event pathway provides a systematic, explicit method of representing different health and social care processes and outcomes. The method involves describing the main pathways of events that have distinct resource implications or outcome values associated with them, from the point of introduction of the interventions, through subsequent changes in management of participants, to final outcomes (see also Chapter 2 of Donaldson (Donaldson 2002)). Figure 15.2.a shows an example clinical event pathway for the clinical event ‘stroke’. In developing a clinical event pathway, it is again important to consider the key issues of magnitude, time horizon and analytic viewpoint.
Once the role and relevance of economic issues has been considered carefully, one or more economic questions, or objectives, can be formulated. Review authors should avoid asking economic questions of the form ‘What is the cost-effectiveness of intervention X (compared with Y or Z)?’, since a critical review of health economics studies is unlikely to provide a credible answer to this type of question that is applicable across settings. Economic questions, or objectives, should be stated explicitly in the Objectives section of the protocol for a review, alongside other research questions and objectives.
Considerations of the role and relevance of economic issues can also be used to inform a commentary on economic aspects of interventions, to be included in the Background section of the review.
An ‘economics commentary’ can be included whether or not the authors intend to incorporate a critical review of health economics studies. This is useful to help set the interventions being studied in an economics context by highlighting their potential economic consequences for consideration by end-users of the review. The ‘economics commentary’ may highlight the economic burden of the illness or medical condition being addressed by interventions, the types of resources required to implement and sustain interventions (resource inputs), the potential impacts of interventions on the subsequent, downstream use of resources (resource consequences) and issues of cost-effectiveness. The commentary should be supported by appropriate references to, and critical comment on, relevant literature wherever possible. Box 15.2.a shows some examples of this type of commentary, extracted from Background sections of current Cochrane reviews.