assessing quality of life in patients with epilepsy

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REVIEW ARTICLE Phar m ac oEc onomlcs 1996 M ay ; 9 (5): 399-416 117D-7690/96/ 0C1J5.(JJ99/$OOJYJ/O © AdisInternational l imited . AI rights reserved. Assessing Quality of Life in Patients with Epilepsy Ann Jacoby Centre for Health Services Research, University of Newcastle upon Tyne, Newcastle upon Tyne, England Contents Summary . 1. Conceptualisation of Quality of Life In People with Epilepsy . 2. Methodological Issues In Assessing Quality of Life in Epilepsy 2.1 From Whom Should Quality-of-L1fe (QOL) Data be Collected? 2.2 Which Dimensions of Quality of Life Should be Measured? 2.3 Which is the Appropriate Instrument to Use? . 2.4 Isthe QOL Instrument Psychometrically Sound? . 2.5 What are the Practical Issues in QOL Assessment? ..... 2.6 Examples of Available QOL Instruments for People with Epilepsy 2.7 Assessing Quality of Life in Children . 2.8 The Role of QOL Assessment In Clinical Settings . 2.9 QOL Assessments as Part of Economic Evaluation 3. Conclusions .................'. ....... 399 400 401 401 . 403 · 403 · 404 . 405 . 407 · 410 410 412 412 Summary The importance of quality-of-life (QOL) assessments in providing quantified information about the impact of chronic illness and its treatment is now generally accepted. For epilepsy, QOL assessment is a relatively recent development, but it is increasingly included within clinical trial protocol s. Clinical trials in epilep sy that have included a comprehensive QOL assessment, although still relatively few in number, have examined the effectiveness both of broad management policie s and of individual drug therapie s. There are a number of important conceptual, methodological and practical issues behind the measurement of quality of life as an outcome of care in epilep sy that are being addressed through current efforts to develop standardised QOL instruments. In trying to assess quality oflife in epilep sy, as in any other condition, it is important to satisfy the universal requirements of a scientific instrument - that it be valid, reliable , sensitive to change and practical. To date, the main 'formal' approaches to QOL assessment in epilepsy have involved the develop- ment of a novel QOL measure from first principles, customising of a previously developed generic measure, identification of a battery of generic and disease- specific scales addressing specific QOL domain s, and adoption of an individual patient-generated approach. These various efforts have produced a battery of potentially valuable tools and approaches. Although QOL assessment is now firmly on the epilepsy research agenda,

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Page 1: Assessing Quality of Life in Patients with Epilepsy

REVIEW ARTICLE Pharmac oEconomlcs 1996May; 9 (5): 399-416117D-7690/96/0C1J5.(JJ99/ $OOJYJ/O

© Adis International l imited . AI rights reserved.

Assessing Quality of Life in Patientswith EpilepsyAnn Jacoby

Centre for Health Services Research, University of Newcastle upon Tyne,Newcastle upon Tyne, England

ContentsSummary .1. Conceptualisation of Quality of Life In People with Epilepsy .2. Methodological Issues In Assessing Quality of Life in Epilepsy

2.1 From Whom Should Quality-of-L1fe (QOL) Data be Collected?2.2 Which Dimensions of Quality of Life Should be Measured?2.3 Which is the Appropriate Instrument to Use? .2.4 Isthe QOL Instrument Psychometrically Sound? .2.5 What are the Practical Issues in QOL Assessment? . . . . .2.6 Examples of Available QOL Instruments for People with Epilepsy2.7 Assessing Quality of Life in Children .2.8 The Role of QOL Assessment In Clinical Settings .2.9 QOL Assessments as Part of Economic Evaluation

3. Conclusions . . . . . . . . . . . . . . . . .'. . . . . . . .

399400401401

. 403· 403· 404. 405. 407· 410

410412412

Summary The importance of quality-of-life (QOL) assessments in providing quantifiedinformation about the impact of chronic illness and its treatment is now generallyaccepted. For epilepsy, QOL assessment is a relatively recent development, butit is increasingly included within clinical trial protocol s. Clinical trials in epilepsythat have included a comprehensive QOL assessment, although still relativelyfew in number, have examined the effectiveness both of broad managementpolicie s and of individual drug therapie s.

There are a number of important conceptual, methodological and practicalissues behind the measurement of quality of life as an outcome of care in epilepsythat are being addressed through current efforts to develop standardised QOLinstruments. In trying to assess quality oflife in epilep sy, as in any other condition,it is important to satisfy the universal requirement s of a scientific instrument ­that it be valid, reliable , sensitive to change and practical. To date , the main' formal' approaches to QOL assessment in epilep sy have involved the develop­ment of a novel QOL measure from first principles, customising of a previouslydeveloped generic measure , identification of a battery of generic and disease­specific scales addressing specific QOL domain s, and adoption of an individualpatient-generated approach. These various efforts have produced a battery ofpotenti ally valuable tools and approaches.

Although QOL assessment is now firmly on the epilepsy research agenda,

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400 Jacoby

some important challenges remain to be met. These include the development ofcomprehensive, age-related measures for children with epilepsy, further investi­gation of the psychometric properties of the available measures for adults, issuesof cross-cultural application and use with proxy informants, and the developmentof utility-based measures .

Quality of life is a relatively recent concept, butone whose definition has been the focus of consider­able attention. The work of sociologists and heathpsychologists in the last 2 decades has done muchto advance the debate about the conceptualisationand measurement of quality of life, and it has cometo be seen increasingly as a relevant indicator ofoutcome in the treatment of chronic illness. Thecase for its assessment in medical settings has beenmade by a number of authors.l!"!

The burgeoning interest in quality of life fromboth clinicians and health services researchers hasbeen attributed to cultural and philosophical devel­opments, which have led to criticism of the bio­medical model and the current emphasis on a holisticapproach to patient care,lSI and to the philosophyof 'enlightened consumerism' which permeates mod­em healthcare systems.l'" Financial constraints onhealth services have also precipitated interest inquality-of-life (QOL) assessment. This is becauseenhanced or reduced quality of life represents oneelement in the economic evaluation of new healthtechnologies and care interventions.

Schipper et al.P1have identified a number of sep­arate concepts that have contributed to our currentunderstanding of the term 'quality of life' . Theseauthors concluded that what has emerged fromthese various attempts at its conceptualisation is afunctional definition that is measurable, evaluativeover time, subjective, and incorporates 5 broad do­mains: physical, occupational, psychological, socialand somatic.l"! In the medical setting, QOL assess­ments can thus be seen as providing quantified in­formation about the degree to which a chronic con­dition and its treatment are perceived by the patientas enhancing or detracting from his or her abilityto function across these various domains at differ­ent stages in his or her illness.

© Adis International Limited . All rights reserved.

Although lagging behind other major chronicconditions in this regard, the assessment of qualityof life as an outcome of medical care for epilepsyis receiving increasing emphasis, perhaps mostnotably within the framework of clinical trials ofnovel drug therapies. Recognition of its potentialvalue is well illustrated by a recent workshop andpublication.l ''! which were dedicated to the topicand were generated by the expectation that QOLoutcomes will be an increasingly important para­meter in epilepsy research and in the future alloca­tion of healthcare resources.

This review addresses some conceptual and theo­retical issues behind the measurement of quality oflife as an outcome of care in epilepsy, the mainmethodological issues in developing appropriatemeasures to do so, and the practical issues in ap­plying such measures, particularly within the frame­work of clinical trials of specific treatments ormodes of delivery of care. In doing so, it draws onexamples from the literature of recent studies ad­dressing quality of life in epilepsy, and highlightscurrent efforts to develop standardised QOL instru­ments. Much of the work to date has focused onQOL assessment in adults, and this is inevitablyreflected in the examples cited. However, someconsideration is also given to the complexities ofassessing quality of life in children and the attemptsto date to address these.

1. Conceptualisation of Qualityof LifeIn People with Epilepsy

The term 'quality of life ' entered the epilepsyliterature only very recently - Hermann'?' traces itsfirst formal application to the proceedings of a UKRoyal Society of Medicine Round Table, held in1990, entitled Quality of Life and Quality of Carein Epilepsy.I 101 However, research into QOL issues

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in epilepsy, although less advanced than in someother chronic conditions, is not new : Scambler!'!'points out that what he refers to as 'pre-formal stud­ies' of quality of life in epilepsy are centuries old.MeadorlP' cites examples of ' for mal' studies dat­ing back to the 1960s, which, although they cannotalways be regarded as comprehensive and system­atic in their approach, did nonetheless constituteQOL assessments.

What such early studies did was to highlightQOL issues specific to individuals with epilepsy,when compared with those with other chronic con­ditions, or in good health. They demonstrated thatwhat Taylorl131refers to as the 'particular predica­ment' of epilepsy includes: (i) the unpredictabilityof seizures, and the consequent increased risks ofinjury and mortality;'!"!" (ii) the adverse effectsof anticonvulsant medications on mood and cogni­tive function;118-211 (iii) the social burden of epi­lepsy, which rests both on the limitations imposedby statute and those imposed by prejudice, fear andlack of understanding on the part of others;122-251

and (iv) the impact of living with a stigmatisingcondition on psychological well-being.126-301

In trying to formally conceptualise these vari­ous aspects of epilepsy, a number of authors havedrawn on a framework first suggested by the WHO(1947) definition of health as 'a state of physical,mental and social well-being and not merely theabsence of infirmity and disease' .1311 The repre­sentation of quality of life by these 3 broad domains- physical, social and psychological - forms thestarting point for the work to develop an epilepsy­specific QOL model1321and a comprehensive QOLinventory for epilepsy.F'l

-More recently, WHOl 341 has defined the conse­quences of disease at the level of impairment (anyloss or abnormality of psychological , physiologi­calor anatomical structure or function) , disabil ity(any restriction of ability to perform an activity inthe manner or range considered normal) and handi­cap (a disadvantage for a given individual , result­ing from an impairment or disability, that limits orprevents the fulfilment of a role). It is from thisconceptualisation that Kendrick and Trimblel351

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cho se to progress to their repertory grid QOL as­sessment. The WHO classification of impairment,disability and handicap is a useful one, in that itemphasises the societal basis of handicap, which,in a historically stigmatising condition such as ep­ilepsy, may be considerable.

The question of whether QOL assessment inchronic illness should embrace all possible do­mains of quality of life, or focus only on those thatare health-related, has been much debated.136-381 Avaluable discussion of this conceptual issue in re­lation to epilepsy is provided by Hermann.l?' Heargues for a broader vision of quality of life,since the nature of this condition means that anyassessment must encompass both ' within-the-skin'(e.g. physical function, emotional state) and 'be­yond-the-skin' (e.g. role activities, social function­ing) variables. Hermann's list of essential domainsfor people with epilepsy covers symptoms, func­tional status, social functioning, sleep and rest,energy, health perceptions, general life satisfaction,role activities, emotional state and cognition.l?'

2. Mefhodologicattssues in AssessingQuality of Life in Epilepsy

There are a number of important methodologi­cal issues in assessing quality of life in people withepilepsy, including:• from whom should such data be collected?• which dimensions of quality of life are relevant,

given the nature of the study in which the assess­ment is to be included?

• which instrument is appropriate to measure thesedimensions, and is the chosen instrument psycho­metrically sound?

• what practical considerations need to be givento making the assessment?

Each of these issues is considered in turn below.

2,1 From Whom Should Quality-ot-Lite(QOL) Data be Collected?

The earliest QOL measures were designed to becompleted by physicians or other health profession­als. Historically, clinicians have been suspicious ofpatient-based assessments of treatment outcome,

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which they have regarded as 'soft data' and there ­fore lacking reliability.l '?' However, studies suchas those by Evans et al.1401and Slevin et al.,1411

which showed that inter-rater agreement about pa­tients' functioning is often poor, and which foundwide discrepancies between the assessments madeabout patients by clinicians and those made by thepatients themselves, resulted in a philosophicalshift in QOL assessment. Thus, it is now generallyagreed that judgements about the way in which ill­ness and treatment affects quality of life should bemade by patients themselves.

Hunt l421asserts that quality of life 'refers essen­tially to a subjective assessment of the situation bythe patient - the only person with sufficient relevantknowledge to make that assessment' . Followingfrom this position, most recently developed QOLassessments for epilepsy are intended for self­report by patients.132.33.35,43,441

Of course, there will be situations in which, forone reason or another, patients are unable to respondfor themselves; in such cases, it will be necessaryto obtain 'proxy' information from a relative, friendor formal carer. For example, obtaining meaningfulresponses to QOL scales from individuals with ep­ilepsy who are also learning impaired is fraughtwith methodological difficulties, and observationalstudies, though more appropriate , are often imprac­tical.

For these reasons, a recent multicentre clinicaltrial assessing the impact of a novel anticonvulsantdrug on the quality of life of children and youngadults with epilepsy and learning impairment madeuse of a parent-completed questionnaire.PU Theparents were asked to complete a battery of scalesand single items to assess seizure severity, seizure­related injuries, adverse drug effects, mood andbehaviour, and overall quality of life. Results of apilot study to examine the psychometric propertiesof the instrument showed that all the scales hadhigh reliability (both internal consistency and test­retest) and good validity. As yet, information aboutresponsiveness is unavailable, but results of thetrial will be published this year, and will providesome evidence of this .

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Jacoby

Children comprise another patient group inwhom obtaining proxy information may be theonly viable approach. Pre-schooI-age children willbe unable to express themselves verbally and mayhave inaccurate recall of even fairly recent events,and school-age children may have difficulty in fill­ing in forms and schedules, or may be intimidatedby being asked questions by a researcher. For suchreasons, QOL data for children with epilepsy, inalmost all studies to date, have been obtained fromprofessionals such as teachers or from parents,most often mothers, rather than from the childrenthemsel ves.146-491

Austin and Dunn (50I have attempted to collectsome QOL information from children aged 8 yearsand over with epilepsy, using self-report question­naires, but this remains an area in which much moredevelopmental work is required.

The limitations of using proxy data have beeninvestigated by Hays et al.,1511 who examined thelevel of agreement between the self-reports ofqual­ity of life of 292 adult patients with epilepsy andthe respective QOL reports completed by their de­signated proxies. Patients and proxies both com­pleted an 89-item QOL inventory, and the resultsrevealed only modest correlations between the 2sets of responses. Not surprisingly, agreement wasbetter for directly observable measures of functionthan for the more subjective measures, and lack ofagreement was sufficiently large in some domainsto introduce bias.

Although I am unaware of any parallel work inchildren with epilepsy, it has been shown thatamong children with other chronic conditions,there are similarly modest agreements betweenparent reports and those of the children themsel ves,agreement being best for issues such as physicalfunctioning and the experience of symptoms, andworst for social and emotional functioning.t'<l

It has also been reported that different proxieswill make different QOL assessments. For exam­ple, Eiserl53J compared mothers' and fathers' rat­ings of the severity ofasthma in their pre-school-agechildren, and found no significant correlation be­tween them. Mothers and fathers have also been

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shown to differ in their assessments of the limitationsimposed by their child's condition.154.551

2.2 Which Dimensions of Quality of LifeShould be Measured?

There is now fairly clear agreement in the liter­ature that quality of life is a multidimensional con­cept, incorporating a number of core domains (seetable 1).1561However, it may be inappropriate withinclinical settings to always measure all domains.Deciding precisely which dimensions of quality oflife to measure will depend on a number of factors,including the nature of the population and condi ­tion under study, the source of the data, the predictedcosts and benefits of treatment, and the length ofthe observation time .157)

For example, within the domain of physicalfunctioning, pain will be much less significant topeople with epilepsy than those with arthritis. Fur­thermore, it is unlikely that a person's occupationalstatus will change during the course of a short termclinical drug trial. What is measured will also de­pend to some degree on the availability of suitableinstruments and the environment in which themeasurement will be conducted.Pf

Consideration should be given to the burden onrespondents, particularly those who are ill, of com­pleting lengthy QOL assessments . Researchers haveto aim for assessments that are comprehensive inrelation to the question being asked, yet simple tocomplete and brief.

2.3 Which isthe Appropriate Instrumentto Use?

Spitzer,1591 in a keynote speech at an internationalconference on QOL measurement held in Portugalin 1986, argued that there was a need for generallyaccepted 'gold standard' QOL and health statusmeasures, developed by a small and select band ofresearchers and subsequently made available to thewider research community. To some extent this hashappened, with the widespread adoption in healthservices research of health status measures foradult patients, such as the Nottingham Health

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Profile'P''! and, latterly, the Short Form 36 (SF-36)Health Survey .l''!'

However, it has been argued that the 'complex­ity of QOL as a phenomenon militates against asingle assessment instrument applicable in all cir­cumstances' ,1621 and it seems unlikely that, at leastfor the foreseeable future , any single QOL measurewill gain universal acceptance either in epilepsy orany other condition.

2.3. 1 Generic versus Disease-Specific MeasuresThe appropriateness of QOL instruments that

are generic versus those that are disease-specific hasbeen considered by a number of authors.138.63.641

Generic measures are designed to cover thecomplete spectrum of function, disability and dis­tress relevant to quality of life and to be applicableacross different types and severities of disease anddifferent medical treatments or health interven­tions. Their advantage is that their psychometricproperties are established and allow comparisonsto be made across different populations and clini­cal conditions. Their disadvantage is that, becauseof their generic nature, they may be insensitive tothe particular problems and outcomes associatedwith specific conditions and treatments.

Developing measures that are specific to partic­ular diseases or populations may appear clinicallymore sensible, but they too have their shortcom­ings. Kaplanl651 points out that disease-specificmeasures are weak from a policy perspective, in as

Table I. Core domains of quality of life (reproduced with kindpermissionfrom Fallowfieldl56))

Core domains Typical items

Psychological Depression

Anxiety

Adjustmentto illness

Social Personaland sexual relationships

Social and leisureactivities

Occupational Ability to carry out paid employment

Ability to cope with householdtasks

Physical Pain

Mobility

Sleep

Appetite

Sexual functioning

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much as they preclude the possibility of comparinghealthcare programmes directed at different diseasepopulations. Nonetheless, disease-specific meas­ures have been shown to be useful in clinical trialsacro ss a range of conditions,166-681and their numberhas increased exponentially since Karnovsky andcolleaguesls"! developed the performance index.Again , epilepsy lags behind other chronic condi­tions in this respect, and epilepsy-specific QOLmeasures have only relatively recently begun to bedeveloped.133.44.70-721

2.3.2 Customised MeasuresAssuming disease-specific measures are avail­

able, and acknowledging the strengths and weak­nesses of both generic and disease-specific meas­ures, it has been argued that the most satisfactoryapproach to QOL assessment is to use a standardcore instrument with customised additions, depend­ing on the particular problem and setting.1571

This approach has been adopted by researchersin epilepsy. For example, Jacoby et al.1431 andBaker et al.!321 used a standard health status mea­sure, the Nott ingham Health Profile, together witha battery of other scales and items that addre ssedQOL domains that were identified, both from theliterature and through pilot qualitative work, as be­ing of particular significance to people with epi­lepsy. Likewise, both the Epilepsy Surgery Inven­tory (ESI-55)1441and the Quality of Life in EpilepsyInventory (QOLIE-89)1331 have taken a core genericmeasure, the SF-36, and appended further epi­lepsy-related items to produce a condition-specificinstrument.

For children with epilepsy, the dearth of generichealth status instruments makes such an approachmore difficult, although some work is now beingdone to address this gap in QOL assessment.F'T'!

2.4 Isthe QOL InstrumentPsychometrically Sound?

Because QOL instruments are used in clinicalpract ice and research to discriminate among indi­viduals or groups of patients, to predict outcome orprognosis and to evaluate within-patient changeover time, a basic requirement is that they be valid,

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Jacoby

reliable and responsive. The meaning of these termsis addres sed in detail in all the standard textbookson outcome measurement,139,76-79! and so will betouched on only briefly here.

2.4. 1 ValidityValidity is concerned with whether or not an in­

strument measures what it purports to measure, andrelates to other variables in previously hypothesisedways. There are a number of different aspects ofvalidity, including:

(a) face validity - does the instrument, on theface of it, appear to be measuring what it was in­tended to measure?

(b) content validity - does it cover the full rangeof relevant topics?

(c) construct validity - does it relate to othermeasures in a manner consistent with previouslyconstructed theoretical hypotheses? For example,does a scale to measure disease impact distinguishbetween groups of patients with differing diseaseseverity?

(d) criterion validity - the relationship of thescale being tested to some other existing measurethat is held to represent a 'gold standard '.

Validity, becau se of the essentially subjectivenature of QOL measures , can be difficult to estab­lish; also, while validity may have been shown forone purpose, it cannot be assumed for all applica­tions.180!

2.4.2 ReliabilityReliability is concerned with the ability of an

instrument to produce the same result s on repeatedoccasions under similar test conditions. If the reli­ability of the instrument is unknown, then any im­provement or deterioration in a patient's quality oflife following a change in treatment or the natureof hislher healthcare might incorrectly be attrib­uted to that change, when in fact it is due to chancefactors.P?'

Reliability is generally assessed in I of 2 ways:(i) by examining internal consistency (the correla­tion , based on a single administration, betweenitems of a scale when randomly divided into 2subscales - otherwise referred to as split-half reli­ability); and (ii) by examining reproducibility

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when the instrument is administered to the samepopulation on 2 or more separate occasions. The bestmeasure of reproducibility (i.e. test-retest reliabil­ity) is the intraclass correlation coefficient, whichis the proportion of variability in the data ac­counted for by differences between individualpatients.P!'

One problem with tests of reliability, to whichStreiner and Normanl'"! draw attention, is that thesignificance of the reliability coefficient is not al­ways readily interpretable, and they note that dif­ferent authors have made different recommenda­tions about what should be seen as constituting theminimum acceptable level of reliability.

2.4.3 ResponsivenessResponsiveness concerns the ability of the in­

strument to detect clinically significant within­patient changes over time, and is a crucial require­ment for clinical trials and evaluation research.Deyo et aL181) point out that descriptions of 'singletime' scale properties, such as validity and discrim­inative ability, are not sufficient to indicate an in­strument's suitability as a measure of change. Amongthe reasons why a QOL instrument may be insen­sitive to change are that:• it includes items not relevant to the particular

disease or treatment group• it includes items focusing on areas where change

would not be predicted within the time frame ofthe study

• it is subject to floor or ceiling effects• it fails to include items that are sensitive to sub­

tle but important changes in patients.P'"Some further statistical caveats are added to this

lis! in the article by Johnson,[82] including: (i) thatuse of simple summary measures may be superiorto more complicated analysis of variance tech­niques; and (ii) that there may be a spurious asso­ciation between change and initial or final value,induced by regression to the mean .

Information about the reliability and validity ofthe various epilepsy-specific QOL measures can bereadily found in the literature. There is generallygood evidence of content and construct validity ofthe measures (table II); however, reporting of test-

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retest reliability appears, for all but the QOLIE-89,to have been confined to Pearson's r rather than thepreferred intraclass correlation coefficient. It ispossible that Pearson's r overestimates the test­retest reliability of a measure as it is not sensitiveto change in the mean score between 2 time points.

Evidence of responsiveness to change in epilepsy­specific instruments is so far generally sparse. Thisis important, since prior knowledge of the respon­siveness of potential instruments would, argueDeyo et aL,181] aid in the selection of measures,permit a more accurate estimation of required sam­ple size and assist in prioritising outcomes to beassessed. More information is needed concerningthe responsiveness of the available instruments tothe changes in functioning and quality of life thatare regarded as significant by clinicians and pa­tients with epilepsy.

2.5 What are the Practical Issues inQOL Assessment?

In addition to these methodological issues, thereare a number of practical problems in QOL assess­ment that need to be resolved, including when andhow to administer the selected instrument.

When to measure quality of life will largely bedictated by the objectives of the study to which itis being applied. Cox et aLlS7) argue that, in a clin­ical trial, QOL assessments should be targeted toreflect the pattern of treatment administration, dis­tinguish early from late treatment effects and con­centrate measurements on strategic time-points,when maximum treatment response is predicted.For example, in a double-blind, placebo-controlled,crossover study of lamotrigine as add-on therapyfor adults with intractable seizures.P'" QOLassess­ments were administered at baseline and at the endof each treatment phase.

The question of how to administer QOL assess­ment will often ultimately be determined by factorssuch as the design of the study and the availablefinancial and manpower resources, but the advan­tages and disadvantages of different modes of ad­ministration - face-to-face or telephone interviews,or self-administered questionnaires, with and with-

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Table II. Summary of evidence for the soundness of the psychometric properties of quality-of-life measures for adults with epilepsy

Jacoby

Instrument Intemal Reproducib ility Content validity Construct validity Responsivenessconsistency

WPSI(83)

Social Effects Scale(84)

ESI-55(44)

QOLlE-89[331

Liverpool Battery

Seizure Severity Scale171)

Impact of Epilepsy Scalel72)

Mastery Scale[8S!

Self-Esteem Scale[86!

Affect Balance Scale(87)

HAD[871

Stigma Scale[881NHp(86)

Life Fulfilment Scale[89!

Adverse Drug Events Profilea

Repertory Grid Assessment[3S1

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a GA Baker, personal communication.

Abbreviationsand symbols:ESI-55 =Epilepsy Surgery Inventory ; HAD =Hospital Anxiety and Depression Scale; NHP =Nottingham HealthProfile; QOLlE-89 =Quality of Life in Epilepsy Inventory ; WPSI =Washington Psychosocial Seizure Inventory ; ,/ =yes; x =no; • =notapplicable because of the nature of the assessment tool.

out respondent supervision - should be carefullyconsidered. To date, relatively little methodolog­ical work has been published that addres ses the rel­ative merits of the various possible approaches, butthere is evidence that quality of responses to arange of health-related questions are unaffected bythe mode of data collection.P'Y"

However, it has been shown that informants aremore likely to divulge sensitive or value-laden in­formation in self-administered questionnairesl94,951

and via telephone, rather than face-to-face, inter­views.1961

There is also evidence that different modes ofapproach produce different responses to multi­category response sets,I971 Administration by mailand telephone of a generic health status measure(the SF-36) in a US population demonstrated thatthe financial costs of data collection were higherfor telephone than postal administration.l'"! In ad­dition, the overall response rate was lower for theformer than the latter approach, whereas for the rateof missing responses for individual items the situ ­ation was reversed.I'<'

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The implications of these various findings, withregard to comparison of results obtained from dif­ferent administration modes, are emphasised byFowler et al.l991particularly for studies where mixedmethods of data collection are being considered.Although multi-mode approaches may appear anattractive and cost-effective solution to the problemof multiple data collection in longitudinal studies,the validity of such an approach cannot be automat­icallyassumed.

Assuming such practical difficulties are resolved,one other issue in QOL assessments, raised by Fowleret al.,1 991 concerns their subsequent interpretation.Once the impact of a treatment policy has beenquantified, researchers and clinicians then have toevaluate its significance, frequently without anyexplicit guidelines about interpretation of scores onthe chosen QOL measures. Clearly, there may bean important distinction between scale score dif­ferences that are stati stically significant, those thathave clinical significance, and those that are signif­icant from the patient's own point of view.

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Quality of Life in Epilepsy

Patrick and Erickson'V' argue that changes indisease-specific scores may be more easily inter­pretable than those in generic scale scores, becausethey will be more closely associated with changesin clinical measures such as disease severity(which, in the case of epilepsy, would be measuredboth by seizure frequency and severity), and becausethey can be compared to assessments of improve­ment made by clinicians and patients. The need forclinically useful interpretation manuals for QOLassessments has recently been highlighted by Wagnerand Vickreyl'P?' and is an area that has still to berobustly addressed in epilepsy.

In summary. the achievement of good QOL as­sessment, in epilepsy as elsewhere, rests on the ap­propriateness and comprehensiveness of the se­lected measure, its psychometric properties, itsbrevity, simplicity and acceptability to patients,and its interpretability. Only by ensuring that as­sessments fulfil these various criteria satisfactorilydo we come somewhere towards making the meas­urement of quality of life, in Spitzer'sl-"! words,'attainable, relevant and scientifically meritori­ous' .

2.6 Examples of Available QOL Instrumentsfor People with Epilepsy

To date, the main formal approaches to QOLassessment in epilepsy are 4-fold:

(a) those that have involved the development ofa novel QOL measure, such as the WashingtonPsychosocial Seizure Inventory (WPSI)170 I or theSocial Effects Scale l841

. (b) those that involve the use of a single pre­viously developed generic profile with customisedadditions, such as the ESI-55 144J or the QOLIEI331

(c) those that make use of a battery of previouslyvalidated scales, addressing specific QOL domains,together with additional disease-specific ques­tions, such as in the studies reported by Jacoby etal.,1431Smith et aI.l901 and Austin and Dunn l501

(d) the patient-generated approach adopted byKendrick and Trimble.P'i'

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2.6.1 Washington Psychosocial Seizure Inventory

The WPSII70 1 is one of the oldest and mostwidely used epilepsy-specific scales that addressesQOL issues . It was designed to evaluate the psy­chosocial problems commonly seen in adults withseizure disorders, and consists of 132 items across8 scales: family background, emotional adjust­ment, interpersonal adjustment, vocational adjust­ment, financial status, adjustment to seizures,medicines and medical management, and overallpsychosocial functioning.

In their article describing the development ofthe WPSI, the authors were at pains to point outthat it represents a comprehensive, systematic andobjective assessment of psychosocial problems.POI

Their emphasis on the objectivity of the scale is inmarked contrast with present-day emphasis on theimportance of subjective assessment, rendering itperhaps less acceptable philosophically than itwas. The WPSI has also been criticised for its di­chotomous response format, the fact that scalecomposition rests solely on statistical grounds andthe fact that, because it is epilepsy-specific, it doesnot allow comparisons with other nonepilepsypopulations.Hf

Nevertheless, the WPSI remains a much-usedmeasure of psychosocial function, having been thesubject of 48 papers to date.l831 Recently, its au­thors, acknowledging the limitations of the WPSIin relation to concepts of quality of life currentlyproposed in the literature, have developed a 36­item WPSI QOL scale .U''!' As yet, however, thereis little information available regarding its psycho­metric properties.

2.6.2 The Social Effects ScaleThis scale was designed to investigate the social

effects of their condition on adult patients withepilepsy of varying duration and severity.P"! Alarge pool of statements about the impact of epi­lepsy was generated through in-depth interviewswith patients. Both patients and physicians werethen asked to group the statements into distinctareas, and other areas were generated from a searchof the relevant literature. The most commonly usedstatement or statements in each of 21 areas thus

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408 Jacoby

a The QOLlE-31 includes items taken from these scales.

Table III. Domains covered by the Quality of Life in EpilepsyInventory (QOLlE-89) [reproduced with kind permission fromCramerl104~

generated were selected for inclusion in the final42-item questionnaire.

Among the areas covered are: attitude towardsepilepsy and seizures; fear of stigma; concernabout personal and social relationships; lack ofconfidence to perform particular activities; prob­lems with healthcare and medications; emotionalproblems and social isolation. The scale is cur­rently being applied in the UK National GeneralPractice Study of Epilepsy,11021in which newly di­agnosed patients are being followed prospectivelyto examine the perceived impact of their conditionover time.

2.6.3 Epilepsy Surgery InventoryRecently, a generic health status measure, the

SF-36161] has become the basis for a number ofQOL measurement initiatives in epilepsy. For ex­ample, Vickrey et al.[441 elected to use it as the basisof the ESI-55, supplementing it with additionalitems that tap aspects of quality of life identifiedthrough a literature search as being of particularrelevance to patients with epilepsy. To the itemsalready in the SF-36, the authors added 5 itemsrelating to cognitive function, 8 relating to rolelimitations, 4 to health perceptions and 2 to overalllife quality.

The final scale thus includes subscales to assesshealth perceptions, energy and fatigue, overallquality of life, social function, emotional well ­being, cognitive function, physical function, pain ,and role limitations due to physical, emotional and

memory problems. The scale appears to possessgood psychometric properties, but it has yet to beused for its intended purpose, namely a prospectivestudy of surgery outcome.

2.6.4 Quality of Ufe in Epilepsy ScalesThe SF-36 is also the basis for the series of

scales recently developed by the QOLIE Develop­ment Group133.I031 and referred to as QOLIE-89 (17scales, 89 items), QOLIE-31 (7 scales, 31 items)and QOLIE-I 0 (10 items selected from the 7 scalesin the QOLIE-31) . These scales are intended forbroader application in studies of people with epi­lepsy than the surgery-specific scale (ESI-55)developed by Vickrey and colleagues.I''U Thedomains covered by the 2 longer versions of thescale are shown in table III.

Devinsky et al.133) have provided cross-sec­tional data, from 304 adult patients attending 25 USepilepsy centres, to support the reliability and con­struct validity of the measure in its long form (i.e.QOLIE-89). The QOLIE Inventory is seen by itsauthors as having 'great potential for assessing theinfluence of treatments and interventions on gen ­eral life sat isfaction ' ,1 121 but its very recent de­velopment so far precludes any judgement of itsusefulness relative to other approaches.

2.6.5 A Health-Related QOL Model for EpilepsyRather than developing a single QOL scale to be

applied across all studies of epilepsy, a group ofresearchers based in Liverpool, England, has de­veloped an epilepsy-specific QOL model 132) thatallows different combinations of domain-specificscales to be applied, depending on the particularresearch question under consideration (table IV).In specifying the model, the authors drew on theformat suggested by Meenan et aJ.,lllOI who iden­tified an operational level at which considerationis given to the impact of epilepsy on a person'sphysical, social and psychological function; and aninstrumental level, at which scales considered ap­propriate to assess these effects are specified.

Where appropriate and psychometrically soundscales existed, they have been utilised; where theydid not, the group have developed them de novo.1321

Although not all were originally developed for

Memory

Language

Medication effects"

Social support

Social function"

Social isolation

Health discouragement

Sexual function

Overall health"

Health perceptions

Seizure worry"

Physical function

Role limitation - physical

Role limitation - emotional

Pain

Overall quality of life"

Emotional well-being"

Energy/fatigue"

Attention/concentration"

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Quality of Life in Epilepsy 409

Table IV.Liverpool quality-ol -meassessment battery lor epilepsy[321

Scale No. of Relerenceitems

epilepsy, each of the scales in the model has beenvalidated in patients with epilepsy. Perhaps themost valuable, and certainly the most widely ap­plied, of the novel scales is the Seizure SeverityScale,1711 which has been used in a number of sub­sequent clinical trials of novel anticonvulsantdrugs. This group of researchers has also devel­oped scales to assess the patient-perceived impactof epilepsy on daily functioning.Ut' feelings ofstigma associated with epilepsy,ISS Iand an adversedrug effects profile (G.A. Baker, personal commu­nication) .

2.6.6 A Patient-Elicited Approach toQOL Assessment

Some researchers (see, for example, O'Boyle etaLIIIII and Ruta et aJ.l1121) have taken issue with thestandard approach to QOL assessment employedin the examples in section 2.6 on the grounds that- since most QOL measures are developed througha process in which the researcher determines thecore dimensions, domains and items to be addressedand the weightings attached to each - an externalvalue system is imposed on patients, which fails totake full account of the individual nature of qualityof life. They have, therefore, tried to develop apatient-elicited approach to QOL assessment.

In the field of epilepsy, a patient-generated ap­proach has most notably been espoused byKendrick and Trimble.P>' who have used a reper­tory grid technique to determine, within 5 core

Seilure Severity Scale 19

Nottingham Health Profile 38

Hospital Anxiety and 14Depression Scale

Affect Balance Scale 10

Sell-Esteem Scale 10

Mastery Scale 7

Stigma Scale 3

Lile Fulfilment Scale 26

Impact 01Epilepsy Scale 10

Adverse Drug Events Prolile 19

71

105

106

107

108

109

8889

72

GA Baker, personalcommunication

areas (physical, cognitive, social, emotional andeconomic), what specific aspects of functioningare important to individual patients. Within thisframework, patients then design their own QOLschedule, rating the degree to which each aspectthey have identified is currently problematic. Inaddition, they are asked to rate other situations andpersons, to construct a 'grid' of their view of theircurrent situation, in relation to their past, expecta­tions for the future and others.

One notable aspect of the method used byKendrick and Trimblel'"! is that, although patientsthemselves identify constructs, the procedure forgetting them to do so is repeated until at least 2constructs in each of 5 key areas of quality of lifehave been elicited. In this sense, the approach isperhaps less clearly patient-generated than its authorssuggest, but it nevertheless permits a more in­dividualised (though somewhat labour-intensive)assessment than standardised scales.

2.6.7 Comparison of Various MeasuresRecently, some attempts have been made to

compare the psychometric properties of these var­ious QOL measures. For example, Langfitt' I 131compared the reliability and validity of the ESI-55 ,WPSI and a generic measure, the Sickness ImpactProfile (SIP),11141 in 71 patients. They found thatinternal consistency reliability was adequate for allthree, but the WPSI had poorer face, content andcriterion validity than either the ESI-55 or SIP. Theauthor concluded that, as its focus is narrower, theWPSI provides a less valid description of theimpact of epilepsy on quality of life than the other2 measures, which are consequently likely to bemore sensitive to overall QOL differences whenexamined as outcomes in clinical trials .

The usefulness of a battery of generic and epi­lepsy-specific scales, including the SF-36,16 11 theImpact of Epilepsy Scale,I72 1the Liverpool SeizureSeverity Scale.l"!' a modified version of the Mas­tery Scalel 1091and a novel2-item Epilepsy DistressScale, has also been examined.Pv' The aim was toevaluate the practicality and psychometric proper­ties of the measures. Data quality was high and ,with few exceptions, both the generic and epilepsy-

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specific measures satisfied standard psychometriccriteria and were shown to be valid in relation to 2clinical criteria (disease severity and symptoms).

Epilepsy-specific scales were generally best atdiscriminating between groups of patients experi­encing differing disease severity, generic ones atdifferentiating between groups with differing experi­ence of symptoms. As Hays et al.1511 comments,future research efforts in relation to adults with ep­ilepsy might most profitably be applied to furtherevaluation of already available measures, ratherthan to re-inventing the QOL assessment wheel.

2 .7 Assessing Quality of Life in Children

All of the above examples relate to QOL assess­ment in adults with epilepsy and, as noted earlier,parallel work for children is largely lacking. How­ever, interest in developing appropriate measuresappears to be gaining impetus in thi s condition andin others (as evidenced by a recent workshop on thetopic held as part of the Second International Con­ference on QOL Researchj.UP' The theoretical dif­ficulties in assessing quality of life in children aresomewhat greater than in adults, largely because ofthe rapid physical, cognitive and emotional changesthat occur during childhood.F'!

Since it is unlikely that a single QOL assessmenttool can take account of the different developmen­tal phases, a more appropriate approach is to focuson the particular problems and stressors associatedwith each, and so develop a series of age-specificmea sures. Such an approach has been adopted else­where,[116.117] but has yet to be rigorously pursuedfor epilepsy. As mentioned in section 2.1, the as­sumption has generally been made that childrenthemselves cannot or should not be asked to reporttheir quality of life and, by and large, assessmentshave been based on proxy measures. However,Finkll181 has reported serious limitations in usingparents ' reports of symptoms, impairments andother general measures, and recent research sug­gests that even very young children can completesimple questionnaires, given some assistance.UPl

To date, one of the most important contributionsto the development of QOL assessment in children

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Jacoby

with epilepsy is that of Austin and colleagues in theUS.I1191 These researchers examined the impact ofepilepsy across 4 broad QOL domains - physical,psychological, social and educational - using parentand teacher ratings on the Child Behaviour Check­IiSt.11201 They reported that, compared with asthmaticchildren, life quality in epileptic children was sig­nificantly compromised.

A major focus of Austin and colleagues' workhas been the study of factors predictive of adapta­tion to epilepsy, and behavioural problems in chil­dren with epilepsy, and this remains an importantcomponent of Austin's current study of childrenwith newly diagnosed seizures.P?' although it alsoaddresses broader QOL issues. As part of the meth­odological developmental work for these studies,Austin has employed a number of child-reportscales, including assessments of self-esteem,11211 ofconcerns and fears about seizures (J.K. Austin,personal communication) and of attitudes towardsepilepsy,1122] and has demonstrated that valid andreliable data can be obtained from children aged 8years and upwards.

Currently available parent-report mea sures, al­though they do not of themselves represent a com­prehensive QOL asse ssment for children, contrib­ute to the necessary armamentarium. They includea child seizure severity scale,I 1231 scales to assessimpact of childhood epilepsy,149.123 1and a scale toassess restrictions because of epilepsy.' 124J As de­scribed in section 2.1, Baker et a1.145] have also re­cently developed a parent-report QOL measure fora very specific subgroup of children with epilepsy- namely, patients with severe epileptic syndromeswho have accompanying learning difficulties.

2 .8 The Role of QOL Assessment inClinical Settings

There has been a large number of studies, bothqualitative and quantitative, that have describedthe quality of life of adultsI23.25.30,125] and chil­drenl46,I19,I261 with epilepsy. Recently, however,QOL assessments have been recognised as havinga useful role beyond being merely descriptive, asmeasures of outcome in studies that seek to answer

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Quality of Life in Epilepsy

clinical questions about the management of epilepsy.Most commonly, this has been within the frame­work of clinical trials comparing treatments.

However, Wagner and Vickreyl'P!' have recentlypromoted QOL assessment as a routine part of clin­ical practice to :• detect functional limitations and psychological

distress• improve clinician-patient interaction• guide management decisions (including those

relating to nonclinical aspects of epilepsy)• provide information on resource use.

Although some clinical trials in epilepsy haveincorporated assessments of specific aspects offunctioning such as behaviour and cognition.l?' thoseincluding a comprehensive QOL assessment are stillrelatively few in number. The latter include thosethat have examined broad management policies,such as the UK Medical Research Council (MRC)Study of Antiepileptic Drug Withdrawal .l'l'! theongoing MRC study of immediate versus delayedtreatment for early epilepsy and single seizures;1481and studies that have examined the effectiveness ofindividual drug therapies, such as the studies oflamotrigine and felbamate used as add-on therapyin patients with intractable epilepsy.145.90. 1271

The trial reported by Smith et al.1901was a placebo­controlled study that examined the impact oflamotrigine not only on seizure control , but also onpatient-perceived seizure severity, psychologicalwell-being, general health status and activities ofdaily living. Consistent with previous trials of thedrug, lamotrigine markedly reduced seizure fre­quency compared with placebo. Patients treatedwith lamotrigine reported significant improve­ments in affect balance and sense of mastery, whichmultiple regression analysis confirmed were inde­pendent of any reduction in either seizure fre­quency and severity. Patients electing to continuelamotrigine therapy after the end of the trial re­ported improved psychological well-being, com­pared with those electing to withdraw, confirmingthe importance of factors other than seizure controlin patients' decision making about their continuingtreatment.

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411

The MRC Antiepileptic Drug WithdrawalStudy ll 281 was concerned not with the comparisonof one drug with another, but of any drug withnone. Its results are therefore very relevant to the70% of patients who become seizure-free aftercommencing anticonvulsant treatment, and forwhom the question then arises of whether or not towithdraw from medication. The authors addressedthis issue by comparing seizure control , and thepsychosocial risks and benefits, resulting from pol­icies of slow withdrawal or routine maintenancewith anticonvulsant therapy. Areas of quality oflife investigated were affective state and sense ofwell-being, social adjustment, social networks andsupport, leisure activities, recent employment his­tory and feelings of stigmatisation.

Although there was a significant clinical riskassociated with the policy of slow withdrawal ofanticonvulsants (the risk of a seizure recurrencebeing almost double for those who withdrew thanfor those who remained on medication), there wereno important differences on any of the QOL do­mains examined between patients remaining on ,and patients withdrawing from , anticonvulsants.P'"As measured by the relative risk on the variousmeasures, the effect of withdrawing from anticon­vulsants was small. The authors of the studyl431concluded that this was because there was a cost topatients ' life quality of taking anticonvulsants,which had not been previously quantified and con­sequently may have often been overlooked by cli­nicians.

The findings from such studies have providedthe impetus for a number of subsequent clinicaltrials in epilepsy that have incorporated QOL as­sessments. One study referred to earlier in this ar­ticle (see section 2.1), and of particular interest,concerns the use of lamotrigine as add-on therapyin children with severe epileptic disorders.Ht' Thenature and frequency of seizures in this populationmean that for them the traditional outcome, seizurecounts, may be particularly unhelpful , and QOLassessment may therefore be of even greater rele­vance. The proliferation of anticonvulsant drugtrials that include QOL assessments indicates a

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much clearer recognition on the part of cliniciansand the pharmaceutical industry to try to quantifywhat was previously deemed unquantifiable.

2.9 QOL Assessmentsas Part ofEconomic Evaluation

In the clinical trials cited above (see section2.8) , QOL assessments were descriptive and thedata presented in disaggregated form. Developingmethods to assign an aggregated value to any de­tected QOL changes, to provide an unambiguousanswer as to which of a number of alternative treat­ments is preferred, has been the focus of interestof health economists; most would argue that eco­nomic evaluations of healthcare interventionsshould involve some form of health state prefer­ence evaluation.UP?' In epilepsy, health economicassessments are notable for their absence, andthose that have been undertaken so far are limitedto calculation of the direct and indirect monetarycosts of epilepsy.l' P?'

Recently, a utility-based methodology, the Q­TWiST (Quality-adjusted Time Without Symp­toms and Toxic ity) has been developed,! 1311 whichits authors claim will permit results from standardQOL instruments to be translated, through mathe­matical modelling, into preference weights . How­ever, the Q-TWiST methodology has yet to be fullydeveloped and applied empirically.

3. Conclusions

Historically, because QOL assessment was con­cerned with the apparently unmeasurable, it wasconsidered to yield scientifically 'soft' data, of lit­tle value to clinicians. Fitzpatrick et al.180) note that,even now, many clinicians exhibit enthusiasm forthe potential relevance of QOL measures, but at thesame time express a number of unresolved doubts.However, QOL assessments are now generallyrecognised as representing a valuable measure ofhealth outcome, particularly in clinical trials com­paring treatments or healthcare programmes, andare being used with increasing frequency.

It has been argued that 'efficacy' protocols thatdo not include attention to QOL factors do a serious

© Adis Intemational Umited. All rig hts reserved.

Jacoby

disservice to patients. I 1321 In trying to assess qualityof life within this or any other framework , it is im­portant to satisfy the key universal requirements ofa scientific instrument; that is, it should be valid ,reliable, sensitive to change, and practical. Pre­cisely which aspect s of quality of life we choose tofocus on or emphasise will depend on the conditionunder study and the nature of the investigation; thelatter will also determine, to a large extent, themethodology adopted to make the QOL assess­ment.

Although researchers in the field of epilepsy ap­pear to have lagged behind others in the area ofQOL research.I'" it is safe to say that QOL assess­ment is now firmly on the epilepsy research agenda:Recent efforts to develop formal, quantitative as­sessments of QOL outcomes in epilepsy have pro­duced a battery of potentially valuable tools andapproaches. However, a number of important is­sues remain unresolved: in particular, there is scantevidence of the responsiveness of the availablemeasures, of their cross-cultural applicability, andof their validity when completed by proxy inform ­ants. There have been no empirical attempts toapply utility-based measures, and the developmentof QOL measures for children with epilepsy lagsbehind that for adults . Growing interest in theseareas among clinicians and health services re­searchers will hopefully go some considerable waytowards answering these questions, and so to en­suring more effective and acceptable care for thosewith epilepsy.

Acknowledgements

I would like to thank Dr Gus Baker at the Department ofNeurosciences, Walton Hospital, Liverpool, England ; and, atthe University of Newcastle upon Tyne, Dr David Parkin(Department of Epidem iology and Public Health) and NickSteen (Centre for Health Services Research ) for their helpfulcomments on the manuscript .

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Correspondence and reprints: Dr Ann Jacoby, Centre forHealth Services Research, 21 Claremont Place, Newcastleupon Tyne NE3 4HB, England.

University ofTromse, Norway

Health Economics Course

for EconomistsThe University of Tromse is planning its sixth distance

learning course in health economics for economists

Starting: September 1996Course director: Professor Gavin Mooney

For further information, please contact ;Sissel Andersen

Instit ute of Community MedicineUni vers ity of Tromse

N-9037 'IrornseNorway

Phone; +47 77644819; Fax : +47 776 44831

Closing da te for applica tions: 15 June 1996

© Adis Internationai Limited . All rights reserved. PharmacoEconomics 1996May; 9 (5)