HEALTH ECONOMICS

Health Econ. 11: 17–19 (2002)

DOI:10.1002/hec.669

DEBATE

Measures of health-related quality of life in an imperfect world:a comment onDowie

John Brazier*,1 and Ray Fitzpatrick21Sheffield Health Economics Group, School of Health and Related Research, The University of Sheffield, UK2Department of Public Health, Institute of Health Sciences, University of Oxford, UK

Professor Dowie has written an interesting andthought provoking paper on a long lasting debatein the literature on measuring health relatedquality of life. The debate between generic andcondition specific measures (CSMs) has notprogressed a great deal with time and he isright to question a purely psychometric approachthat currently tends to focuses on effect sizes.He has also presented an interesting challengeto the compromise solution suggested by a numberof psychometricians to adopt both types ofmeasure.

The paper is predicated on the apparently usefuldistinction between knowledge- versus decision-validity, but this is something of a straw manargument. Advocates of CMSs are not interestedin knowledge-validity but are concerned withdifferent types of decisions. Furthermore, produ-cers of criteria for judging the merits of measures(including ourselves [1,2]) do not presume it to bean absolute question of whether a measure is‘valid’ but hope such lists assist researchers andother users to find the best measure for theirpurpose, such as informing clinical or resourceallocation decisions.

For patients and clinicians important informa-tion is provided by a trial through the use of CSMsin terms of the impact on the problem that theybring to the doctor – i.e. proximal concerns.Neither the patient nor the doctor are necessarilyanticipating an impact on the more distal dimen-sions typically covered by generic measures.Professor Dowie’s response to this narrow viewis that there may be important consequences of the

treatment that are not covered by the CSM andconsequences for co-morbidities. This is the basisof the usual argument for using both types ofmeasure in trials.

Professor Dowie goes on to argue that a genericmeasure ‘is intended to cover the full range ofhealth outcomes’ whereas the condition specific isby definition intended to cover a narrowerrange. On the basis of this distinction of intentionhe argues that in most cases the GEN shouldbe used alone, but he accepts that there may becircumstances where a CSM is preferable, butthat it is never preferable to use both (fordecision-making purposes). We would just like tomake a few comments about this distinction ofintention.

CSMs typically focus on fewer domain ofinterest and hence may be able to ask morequestions about each domain and therebyachieve a greater degree of refinement. Forexample, the EQ-5D has a large jump inscores between perfect health and any levelof illness of 1.0–0.88 and has only two levels ofimperfect health for each dimension. However,Professor Dowie seems sceptical as to theempirical evidence regarding the sensitivity ofCSMs over generics. We agree there are casesthat do not support this common claim in thepsychometric literature [3], but equally there aremany where this has been found including: EQ-5Din chronic pulmonary disease [4] and in cosmeticsurgery [5], the SF-36 in urinary incontinence [6]and the example of urinary incontinence that heprovides [7].

Copyright # 2002 John Wiley & Sons, Ltd.

*Correspondence to: Sheffield Health Economics Group, School of Health and Related Research, The University of Sheffield,Regent Court, 30 Regent Street, Sheffield, S1 4DA, UK. Tel.: 0114 222 0715; e-mail: j.e.brazier@sheffield.ac.uk

The main concern people have with genericmeasures is that their domains are too far removedfrom those of the patient and are often irrelevantto the condition. Even at the level of intention it isnot clear to us that developers of generic measuresintend to cover the full range of health problems.Developers themselves have used terms such as‘core’ [8] or described the content of instruments asaddressing the ‘majority’ of health concerns ofpeople [9]. A better approach would be to conceiveof a matrix of health, where one specific genericmeasure covers Sections A and B, one specificCSM measure covers B and C and so on. TheEQ-5D, for example, does not directly assesscognition, seeing, hearing, sleep, energy or breath-lessness, but these are often the primary problemsof concern to patients

The choice between generic measures and CSMsshould be made primarily on the appropriatenessof the content of the instrument. Given theincreasing emphasis on patient’s views then anobvious group to turn to for advice are thosewhom we expect to benefit (or suffer) from theintervention, rather than impose our own views. Aresearcher will also want to choose the measure (ormeasures) that best covers the domains within theresource available for the study (including the timeof patients or their proxies). This requires someempirical consideration of the responsiveness ofthe measure. Professor Dowie is right to criticisethe psychometric literature on responsiveness, thatis often driven by comparisons of effect sizes.Biggest is not always best. What is required is toexamine the ability of measures to respond tominimally important changes as reported bypatients in health transition questions [10]. Sensi-tivity is important since many trials are examiningsmall and hard to find differences between activetreatments, particularly in the pharmaceuticalsfield.

For social decisions, it might be thought thatthe case for a reliance on generic preference-based measures is much stronger. In order toinclude health related quality of life in aneconomic evaluation, the only rigorous waywould be to conduct a cost utility analysis(CUA) which requires a preference-based measureand since only (some) generic measure arepreference-based then this would seem to ruleout all CSMs.

At a social level, the choice of appropriatedomains is more than simply a matter for patients.Although their views will be important, there is an

additional concern with what represents an appro-priate benefit from public funds. At least in theUK, the reluctance to fully meet patient demandsfor viagra seems to be partly based on this.Similarly debates over IVF services have beenconcerned partly concerned with the appropriate-ness of funding such services from health carebudgets. However, we would contend that most ofthe health domains covered by CSMs and genericswould be regarded as within the legitimate domainof public funding provided there was a healthrelated cause.

One or other type of measure may prove to beunnecessary since it has not picked up any changesor because the generic has been found toadequately reflect the changes in the CSM. Therewill be scenarios, however, where it will benecessary to combine the two measures. ProfessorDowie is concerned with the resultant intuitiverather analytical basis of any decision, since thiscan only be done within the framework of a cost-consequences analysis and this is not usuallyregarded as a technique of economic evaluationat all [11]. We would be more concerned by apolicy of deliberately excluding domains of healthimportant to patients from consideration ofeconomic appraisal on the grounds of analyticalinconvenience.

We agree that in the longer term the solutionwill be to either improve the generic measures bymaking them more sensitive and in some casemore relevant by adding dimensions. It shouldalso be recognised that generics vary in thedomains they cover and a more appropriate choiceof generic may solve the problem in some cases.The HUI-III [12], for example, covers the dimen-sions of cognition, seeing and hearing excluded bythe EQ-5D and SF-6D but not usual activitiesdimension found in the EQ-5D, and neither have adimension for energy, such as the SF-6D [13].Another solution in some cases may be to improveCSMs and extend their coverage to treatmentoutcomes. For social decision-making it is alsopossible to estimate preference-weighted CSMs(for example see the work of Revicki andcolleagues [14], although this raises technicalproblems of combining generic and CSM prefer-ence-based measures where the preference functionis non-additive). For the short term, clinicalresearchers and health economists must workwithin the domain of a considerably less thanperfect world and this may sometimes mean usingboth types of measure.

Copyright # 2002 John Wiley & Sons, Ltd. Health Econ. 11: 17–19 (2002)

J. Brazier and R. Fitzpatrick18

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Measures of HRQOL 19

Copyright # 2002 John Wiley & Sons, Ltd. Health Econ. 11: 17–19 (2002)