Health economic measures in schizophrenia research

Background It is essential in economic evaluations of schizophrenia interventions that all relevant costs are identified and measured appropriately. Also of importance is the way in which costdata are combined with information on outcomes.

Aims To examine the use of health economics in evaluations of interventions for schizophrenia.

Methods A review of the key methods used to estimate costs andto link costs and outcomes was conducted.

Results Costs fall on a number of different agencies and canbe shortterm or long term. Cost-effectiveness analysis andcost–utility analysis are the most appropriate methodsfor combing cost and outcome data.

Conclusions Schizophrenia poses a number of challenges for economic evaluation.

INTRODUCTION

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INTRODUCTION

In evaluating interventions to treat schizophrenia it is clearlyimportant to assess the clinical and social effects of theintervention and to measure these appropriately. It will oftenbe desirable to include a number of outcome measures, rangingfrom those with a relatively narrow perspective (e.g. symptommeasures) to those which are more holistic (e.g. quality oflife measures). Ideally, we would hope that decision makerswould only favour interventions which have proven efficacy.Although good evidence is certainly required for new treatmentsor services, some of those in existence probably do not haveas firm an evidence base.

Evidence that an intervention is effective does not in itselfmean that it should be implemented. All interventions requirethe use of resources (money, time, equipment, etc.), and thesewill inevitably be limited in their supply and able to be usedto provide care in other ways (whether for people with schizophreniaor with asthma, cancer, etc.). Resource scarcity and competing demands for these resources means that the costs of interventionsfor schizophrenia need to be assessed in addition to outcomes.

MEASURING COSTS

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MEASURING COSTS

Costs occur when a productive activity takes place that necessitatesthe use of scarce resources that could be used for some otherpurpose. Economists describe this as an opportunity cost. Thetime that psychiatrists, community mental health nurses, psychologists,social workers and others spend in providing care for peoplewith schizophrenia could be spent with other patient groups,and hence a cost arises. Unpaid care (from families/friends)will also frequently be used, and this also has an opportunitycost.

The focus of economic analyses is often on the final figure(in pounds, dollars, euros, etc.), but this is simply a proxymeasure for care inputs (and in schizophrenia these will bemany) that a patient receives. It is generally incorrect toregard costs as outcomes; rather they are a representation of inputs that produce outcomes. Some of the impacts of interventionsfor schizophrenia can be measured in monetary units, for examplein-patient admissions, if a reduction is the main aim of theintervention, as with crisis resolution teams.

To estimate the cost of schizophrenia care it is necessary toidentify all the resources required to provide this care andalso those resources that are subsequently affected. The costsof treatment with atypical antipsychotics, for example, includenot only the specific drug costs but also the professionaltime required to administer and monitor treatment plus the cost of other care (such as in-patient stays and out-patient appointments)if these may change as a result of the drug treatment.

A common costing perspective in economic evaluations is to includeall health service costs. This is the preferred view of theUK's National Institute for Health and Clinical Excellence(NICE), whose remit is to offer guidance on the spending ofNational Health Service finances. In schizophrenia care eventhis will be inadequate, as interventions which are successful(e.g. in reducing positive symptoms) could alter the use apatient makes of social care, education and criminal justiceservices. Costs to families and friends in terms of the unpaidcare (but representing costly lost opportunities) providedand also the potential value of patient time spent in contactwith services could also be included.

The Client Service Receipt Inventory (CSRI; Beecham & Knapp, 2001)is the most commonly used questionnaire to measure servicecosts for people with schizophrenia. The CSRI is usually completedthrough interviews with patients, although case notes and informationfrom carers can be used, and some versions can be completedby the patients themselves. The information collected with theCSRI, or a similar measure, can be combined with appropriateunit cost information (e.g. Curtis & Netten, 2006) togenerate service costs.

Costing systems of care
Several studies have assessed the economic impact of alternativeapproaches to delivering schizophrenia care. In a review ofhome-based care (assertive community treatment and crisis interventions)Burns et al (2001) identified 22 studies that had includedan economic component. It was encouraging that many of these did take a relatively comprehensive approach to costing andthat this had improved compared with an earlier review (McCrone & Weich, 1996).

Broader studies have attempted to cost the impact of schizophreniaat a national and even international level. Making comparisonsbetween countries presents difficulties given variations inthe methodologies used (Andlin-Sobocki & Rössler, 2005).Differences in price levels generally (and healthcare pricesin particular), the supply of specific services and the structureof mental health services will all affect service costs, aswill variations in patient need. Nevertheless, it can stillbe informative to examine the contribution that specific servicesmake to overall service costs.

In-patient care has consistently been the most costly servicesince deinstitutionalisation began. Knapp et al (2004) reportedthat it accounts for between 28 and 94% of direct healthcarecosts in schizophrenia, whereas medication usually accountsfor less than 15% of costs. One exception was in Nigeria wheremedication accounted for 62% of costs, reflecting the muchhigher drug costs relative to cost of in-patient care in low-and middle-income countries. This is a vivid reminder thatcost findings in one area cannot be simply translated to another.The supply of services will naturally have a major impact onutilisation and therefore costs. In a five-country comparisonof schizophrenia care (Table 1) costs were particularly lowin a Spanish city where there was limited availability of day or residential care (Knapp et al, 2002).

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Table 1 Comparative 3-month costs of schizophrenia care in five European cities¹

Costs of specific interventions
Economic evaluations have been conducted of a wide range ofinterventions for schizophrenia (McCrone & Weich, 1996;Byford et al, 2003). Most tend to concentrate on healthcarecosts, with some also including social care and criminal justiceservice costs. Very few evaluations have assessed the impactthat interventions have on informal care costs, an importantomission as many community-based interventions could well increasethe necessity for care from family members or friends.

Another neglected cost is patient time spent using services.In economics generally, time is valued using information onan individual's wages, but the majority of patients in contactwith specialist services are not in work. However, this doesnot mean that the value of time is zero – time spent onother activities will still have to be forgone in order to useservices. This might be relevant when evaluating assertivecommunity treatment, which is principally targeted at patientswho are `difficult to engage'. Although it is probable thatengagement problems are usually a result of the clinical featuresof schizophrenia, some patients might be engaged in other activities that they value and which limit the time which they wish tospend accessing services (even if this is to the detrimentof their mental health).

Cost information is also relatively limited concerning the periodbefore patients receive care for schizophrenia. The durationof untreated psychosis (DUP) has been reported to be up to1–2 years (McGlashan, 1999). Case-note narratives andstudies of pathways into care suggest that this period is characterisedby contacts with criminal justice services, visits to accident and emergency departments and interruptions to employment.All of these consequences incur costs, and interventions toreduce the DUP should reduce these, but to date no study hascalculated this effect. Further discussion of the DUP is providedby Singh (2007) in this supplement.

Most economic (and clinical) evaluations have relatively shorttime scales. The consequence of this is that the longer-termcost impact of improved, or worsened, outcomes is neglected.If an intervention is successful then it is highly likely thatthis will have a long-term impact on the use and cost of services,especially for people with a long-term condition such as schizophreniawhere some of the care inputs required have particularly high costs. However, the extent of cost savings as a result of successful interventions is unclear. Engagement with services might beenhanced, which could actually increase long-term costs. However,it is probably more likely that effective care will reducethe need for crisis services – and in particular emergencyadmissions – if effectiveness means fewer and less severerelapses.

LINKING COSTS TO OUTCOMES

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LINKING COSTS TO OUTCOMES

The measurement of costs associated with interventions for schizophrenia forms only one component of an economic evaluation. The synthesisof information on costs with data on effectiveness is the essenceof economic evaluation. This is illustrated in Fig. 1 wherecosts (should) depend on patient needs and influence outcomes.There are different forms of economic evaluation and these differ according to how outcomes are measured.

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Fig. 1 Relationship between patient needs, costs and outcomes.

Cost-minimisation analysis
There are some situations where the outcomes of different servicesare known a priori, and therefore only costs need to be measured.If outcomes are identical then the least-cost option is thepreferred one. However, given the variety of possible interventionsfor schizophrenia (typical and atypical antipsychotics, psychologicaltherapies, early intervention, etc.) only rarely will outcomesbe known with confidence beforehand.

Cost-effectiveness analysis
Cost-effectiveness analysis combines cost information with dataon a single condition-specific outcome measure, for examplesymptomatology or social functioning. This form of analysiscan have particular relevance for clinicians. However, it islimited given that schizophrenia affects patients in many ways.This is a common limitation of most clinical evaluations, which generally specify a primary outcome measure.

Cost–consequences analysis
This is a more general case of cost-effectiveness analysis thatreflects the broad impact that interventions have. Rather thanone single outcome measure being used, a number of differentmeasures are considered. Economic evaluations of interventionscould combine cost-effectiveness and cost–consequencesanalyses, with the former conducted using the primary clinicaloutcome measure and secondary measures simply reported alongsidethe cost findings.

Cost–utility analysis
This is similar to cost-effectiveness analysis but uses a genericmeasure of outcome. This enables interventions in diverse areas(e.g. cancer and stroke) to be compared in terms of cost–utilitywith those for schizophrenia. The most common outcome measurein this form of analysis is the quality-adjusted life-year(QALY). Having a generic measure of outcome is of particularimportance for those making recommendations across diverse clinical areas. In the UK, NICE bases many of its findings on the costper QALY achieved by different interventions.

Quality-adjusted life-years are a composite measure of the amountof time spent in a particular healthcare state and the qualityof life experienced during that time. The latter is measuredon a scale from 0 (death) to 1 (full health). The most commonquality of life measure used in economic evaluations is theEuroQoL–5D (EQ–5D; Williams, 1995). This consists of five domains (mobility, self-care, usual activities, pain/discomfortand depression/anxiety) and respondents state whether theyhave no problem, some problems or major problems for each domain.This results in distinct health states to which `utility' orquality of life scores (on a 0–1 scale) are attached.Such scores have been derived from a general population surveywhere people were asked to compare health states with fullhealth (Dolan et al, 1995).

To date, cost–utility analysis has been used infrequentlyin studies of care for schizophrenia. Most QALY measures (suchas the EQ–5D) focus largely on physical health problemsand there are questions about the sensitivity of QALY measuresto changes in mental health states (Chisholm et al, 1997).However, there have been a small number of attempts to use theQALY method in studies of schizophrenia care (e.g. Rosenheck et al, 1998;Sevy et al, 2001) and more work in this area would be useful.

Cost–benefit analysis
Cost–benefit analysis compares the costs of a particularservice with the outcomes achieved also measured in monetaryterms. If the outcomes in monetary terms exceed the costs thenthe service is efficient. One of the very earliest economicevaluations of community mental health services in Madison (Wisconsin,USA) used this method, with earnings from work used as the main outcome measure (Weisbrod et al, 1980). The breadth of waysin which interventions for schizophrenia might affect patientssuggests that cost–benefit analysis will rarely be appropriate.

ANALYSIS AND INTERPRETATION OF ECONOMIC RESULTS

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ANALYSIS AND INTERPRETATION OF...

If a new intervention for schizophrenia is compared with usualcare then a number of results could occur. It would be appropriateto adopt an intervention if it results in lower costs thanexisting care and better outcomes. The intervention shouldalso be favoured if outcomes are no different but costs arereduced or if costs are the same and outcomes are improved.Usual care would be the preferred option if the results werethe opposite way round. However, it is unclear whether or nota new intervention should be adopted if outcomes are betterbut costs are higher. In effect this becomes a value judgement,with the key question being whether or not the increased costsare justified by the level of improved outcomes. Similarly, there is ambiguity about the appropriateness of an interventionif it saves money but is less effective. Interestingly, thereappear to be few studies in this category. Interventions withsignificantly better outcomes than comparators will frequentlyreduce costs (especially those associated with admissions).

Many economic evaluations actually have uncertain results. Forexample, both the UK700 study (Byford et al, 2000) and thePRiSM Psychosis Study (McCrone et al, 1998), which comparedthe costs and outcomes of intensive and standard care servicesfor people with psychosis, found no statistically significantdifferences between costs and outcomes.

To address such uncertainty, it is becoming common practiceto link cost and outcome data from cost-effectiveness and cost–utilityanalyses using incremental cost-effectiveness ratios (ICERs).An ICER is defined as the ratio between the difference in costsbetween two interventions and the difference in outcomes. TheICER then allows us to state the cost that is incurred for an intervention to produce one unit of outcome more than a comparator.An ICER is only informative if one intervention is both moreeffective and more costly than its comparator (otherwise theintervention or the comparator would be the dominant option).Relating incremental costs to incremental outcomes suggests that a unit improvement in outcome (e.g. a 1-point decreasein score on the Brief Psychiatric Rating Scale or the Positiveand Negative Syndrome Scale) has a meaning to decision makers.The latter may not hold and so more tangible outcome measuresmight be preferred (e.g. measuring outcome in terms of number of clinically important changes or number of people above orbelow a particular clinical cut-off point).

One of the problems with ICERs is that they rely on point estimatesof costs and outcomes and yet there will be uncertainty aroundboth of these. This has led economists to produce cost-effectivenessacceptability curves. These show the probability that one interventionis more cost-effective than another for alternative values(thresholds) placed on a unit improvement in outcome.

CONCLUSIONS

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CONCLUSIONS

Since the 1980s there has been a substantial increase in thenumber of studies that have examined the costs associated withschizophrenia and economic evaluations of specific interventionsfor this disorder. The quality of studies has generally improvedbut there are still limitations. In particular, recent methodologicaldevelopments in health economics generally need to be appliedto multi-site studies to generate evidence from the large samplesthat these studies can provide. Schizophrenia affects the livesof patients in many ways and it is essential that outcome measuresused in economic evaluations reflect this. What is clear isthat the costs of care should be measured comprehensively andover an adequate period. Costs also need to be linked to outcomesappropriately. The most suitable methods for doing this appearto be cost-effectiveness and cost–utility analyses.

REFERENCES

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