Understanding and Assessing the Impact of End-Stage Renal Disease on Quality of Life

Understanding and Assessing the Impactof End-Stage Renal Disease on Qualityof LifeA Systematic Review of the Content Validity of Self-AdministeredInstruments Used to Assess Health-Related Quality of Lifein End-Stage Renal Disease

Cheryl Glover, Pauline Banks, Amanda Carson, Colin R. Martin and Tim Duffy

School of Health, Nursing and Midwifery, University of the West of Scotland, Ayr, Scotland

Contents

Abstract. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191. End-Stage Renal Disease (ESRD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202. Quality of Life (QOL) and Health-Related QOL (HR-QOL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

2.1 The Impact of ESRD on QOL. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212.2 The Importance of Content Validity in Assessment of HR-QOL in ESRD . . . . . . . . . . . . . . . . . . . . . . 21

3. Literature Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223.1 Search Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223.2 Content Validity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

4. Generic Instruments Used to Measure QOL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235. Renal-Specific Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Abstract Advances in healthcare, combined with an increasing number of adultswith end-stage renal disease (ESRD), mean that there is a growing numberof people now surviving on renal replacement therapy. The issue of health-related quality of life (HR-QOL) is becoming increasingly important in thisarea. For this reason, the content validity of various instruments used tomeasure HR-QOL in an ESRD population were explored.

Systematic searches of MEDLINE (1950–2009) were conducted usingterms related to ESRD combined with terms associated with measuring HR-QOL. A total of 378 abstracts were identified, detailing the repeated use of sixgeneric measures and four disease-specific measures. The generic HR-QOLmeasures discussed include the Medical Outcomes 36-Item Short Form Sur-vey (SF-36), the EuroQOL 5 Dimension (EQ-5D), and the WHO QOL as-sessment (WHOQOL-BREF). The most frequently used disease-specificmeasure discussed is the Kidney Disease QOL instrument (KDQOL) and itsderivative versions (KDQOL-SF, KDQOL-36).

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The appropriateness of using the SF-36 in this population is challengedand recommendations include using the WHOQOL-BREF in cases when ageneric instrument is required and the KDQOL-SF when a more disease-specific measurement is called for.

1. End-Stage Renal Disease (ESRD)

There are currently over 45 000 people receiv-ing some form of renal replacement therapy in theUK.[1] This number is expected to increase, as ithas done in the past few decades.[2] This increaseis caused by advances in healthcare provision thathave improved survival rates in the end-stagerenal disease (ESRD) population and the rise indiabetes, one of the causes of renal failure. Thesefactors also coincide with the growth of an aginggeneral population, as the incidence of renal fail-ure increases with age.[2]

There are three choices for renal replacementtherapy available to those with ESRD: conser-vative care, dialysis (hemodialysis or peritoneal),or kidney transplant.

Conservative or palliative care is considered incases where dialysis may not prolong life. Suchpatients that may choose to opt for symptomcontrol without dialysis include those who haveextensive co-morbidities or the very elderly.[3]

The two modes of dialysis are very different.Hemodialysis involves transferring blood fromthe body into a dialysis machine, which filtersout waste products and excess fluids before pass-ing this filtered blood back into the body. Formost, this process takes place in a hospital withpatients requiring three sessions of 4–6 hoursper week.

The most common form of peritoneal dialysisis continuous ambulatory peritoneal dialysis(CAPD). This can be performed at home eitherby the patient or a carer and works by using thebody’s peritoneal membrane as a semi-permeablemembrane. A catheter is inserted into the patient’speritoneal cavity into which dialysis fluid is in-fused. Osmosis and diffusion then occur across

the peritoneal membrane. This exchange processtakes approximately 40 minutes and is requiredto be done 3–5 times a day. The dialysis fluid is inplace for approximately 4–6 hours, removed andthen replaced for the process to begin again.Automated peritoneal dialysis (APD) is less com-mon and as such there does not exist a great dealof literature relating to APD and health-relatedquality of life (HR-QOL). APD involves the use ofa machine to fill and drain the abdomen, usuallywhile the patient is asleep.

In addition to the actual dialysis process,ESRD patients are also required to adhere tofluid and dietary restrictions and to take a num-ber of medications.

Transplant provides the best long-term out-come for patients with ESRD. However, theshortage of organs, organ rejection, and the un-suitability of some patients for surgery can meanthat many patients spend a number of years ondialysis.

Patients with any chronic disease face chal-lenges from the disease itself, from side effects,and from other restrictions imposed by treat-ment regimens. Therefore, the aims of chronicdisease management extend beyond the strictlymedical aspects of treatment.[2] In the past 2decades there has been a shift in medicine to theaim of providing more holistic care. In light ofthis, the issue of patient QOL is becoming in-creasingly important and QOL is now an essen-tial outcome in clinical studies. The methods ofmeasuring QOL therefore need to be examinedin terms of their content validity for specificpatient groups such as those with ESRD. Theaim of this review is to examine the contentvalidity1 of self-administered questionnairesused to assess HR-QOL in ESRD.

1 In this context, content validity is defined as ‘‘the degree to which elements of an assessment instrument arerelevant to and representative of the targeted construct for a particular assessment purpose.’’[4] (p. 238)

20 Glover et al.

ª 2011 Adis Data Information BV. All rights reserved. Patient 2011; 4 (1)

2. Quality of Life (QOL) andHealth-Related QOL (HR-QOL)

QOL is a well known and well used phrase.While there have been many definitions proposedfor the term, there is no consensus on the exactmeaning. Bowling[5] suggests that ‘‘in general termsquality can be described as a grade of goodness.’’QOL has been studied in relation to many differentaspects of life, including objective terms such asincome, subjective terms such as happiness andwell-being, and in collective terms such as equal-ity.[6] The definition that seems to encompass allthese aspects comes from the WHO QOL Group(WHOQOL) who state that QOL is an ‘‘y in-dividual’s perception of their position in life in thecontext of the culture and value systems in whichthey live and in relation to their goals expectations,values and concerns y [including] y physicalhealth, psychological state, level of independence,social relations, personal beliefs and their relation-ship to salient features of the environment.’’[7]

HR-QOL narrows the focus to those aspectsof life affected by health, but again there havebeen many suggestions as to definition. However,it should be noted that, in the literature, the terms‘quality of life’ and ‘health-related quality of life’seem to be interchangeable. Many studies use thesame instruments, with some concerning themeasurement of QOL, whilst others state they aremeasuring HR-QOL. However, in clinical set-tings, the use of ‘HR-QOL’ is more appropriatebecause it is the effect of a health state or treat-ment on QOL that is being investigated.

HR-QOL may be studied for many differentreasons, including the comparison of the effective-ness of different treatments, the cost effectivenessof treatments in terms of quality-adjusted life-years(QALYs), and in order to provide a more holisticview of the patient to enable treatment regimens tobe tailored to individual needs. In terms of ESRD,the prospective QOL of the patient is consideredin the decision of treatment modality. QOL hasbecome increasingly important to those caring forpeople with renal disease and there is increas-ing emphasis placed on the importance of usingpatient-reported outcome (PRO) measurements.Self-administered HR-QOL assessments are pref-

erable, as it has been shown that medical pro-fessionals rate the HR-QOL of patients lower thando the patients.[8,9] This is perhaps because medicalprofessionals view the HR-QOL of patients inmore medical terms, such as physical symptoms,whilst the patients view HR-QOL in broaderterms, such as those suggested by the WHOQOL.

The WHO define health as ‘‘a state of com-plete physical, mental and social well-being andnot merely the absence of disease or infirmity.’’[10]

If we are to accept this definition of health,then instruments that concern the measurementof HR-QOL must involve all of these concepts.

In deciding which instrument to use, there aretwo options: generic or disease specific, with ad-vantages to both. Generic measurements can beused to compare across different populationswhilst disease-specific measurements are argu-ably more sensitive to changes and differenceswithin a specific population.

2.1 The Impact of ESRD on QOL

The issue of QOL is significant in all threetreatment choices in ESRD (conservative care,dialysis, and kidney transplant) and the issuesthat arise concerning QOL can be very differentacross the treatment modalities. Hemodialysisand peritoneal dialysis are sufficiently different asto have different impacts on the lives of patientsundertaking them and transplant brings up anumber of QOL issues in itself, which include sideeffects of immunosuppressant drugs, life changes,and fear of rejection.

The issue of QOL is seen as increasingly sig-nificant in the renal population. Identifications ofpredictors of HR-QOL could make it possible tointervene in some way, with the aim of increasingthe HR-QOL in people with ESRD. HR-QOL,whilst an important outcome in itself, is alsoassociated with hospital utilization and mortalityin this patient group.[11]

2.2 The Importance of Content Validityin Assessment of HR-QOL in ESRD

HR-QOL is a particularly important outcomein diseases such as ESRD, where there are a va-riety of co-morbidities and where the disease is

End-Stage Renal Disease and Quality of Life 21


characterized by many different symptoms.[12]

The measurement of HR-QOL has the ability toidentify treatments that may extend life at thecost of QOL or indeed those that have little im-pact on survival but an influence on QOL.[12] Ithas also been suggested that optimizing HR-QOLmight be the most important difference thatthe healthcare team can make to a person withkidney failure.[13] At the present time, HR-QOLmeasures have not been included in routine clin-ical practice, and clinical decisions are routinelybased on judgments of QOL based on the pres-ence of symptoms.[13] This has been shown to bean inadequate representation of actual patientHR-QOL.[8] Family member proxy measure-ments have also been shown to be a poor sub-stitute for patient HR-QOL measurements.[14]

In order to adequately meet patient needs, theassessment should ideally be self-administeredand the tools used must be reliable and valid. Theinstruments used must measure what they set outto measure. There are, of course, many otherpsychometric properties that can be measured,including test-retest reliability and internal reli-ability. These measurements become redundanthowever, if the content is not valid. The followingdiscussion focuses on the main assessment toolsused to measure HR-QOL in renal disease in re-lation only to their content validity.

3. Literature Review

3.1 Search Methodology

The search for relevant literature followed afive-phase approach.� Phase 1. Systematic searches of MEDLINE

(1950–2009) were conducted utilizing thefollowing search strategy: Title = (renal ORkidney OR ESRD OR dialysis OR CAPD)and Abstract = (quality of life OR QOL ORHRQOL OR HRQL) and (measure* OR toolOR scale OR question*). The initial searchwas limited to only those articles published inthe English language and that concerned adulthumans. This resulted in 497 citations.

� Phase 2. The pool of citations was limited toexclude review articles, meta-analyses andarticles relating to oncology and pediatrics

(this resulted in 378 citations). In order to beincluded in the review, the abstract was re-quired to state that a specific instrument wasused to measure QOL.

� Phase 3. The abstracts of the 378 citationswere screened to ascertain which QOL toolswere used.

� Phase 4. To gain additional information aboutthe instruments used, additional searches wereundertaken using the instrument name and ab-breviation alone (for renal-specific measures)or paired with renal search terms (for genericmeasures). From the 378 articles screened, sixgeneric measures commonly used to studyHR-QOL in ESRD and four disease-specificmeasures were identified.

� Phase 5. The generic and disease-specific mea-sures identified were reviewed by the team ofauthors whose expertise includes clinical knowl-edge in relation to renal care and considerableresearch experience of QOLmeasures in a rangeof conditions.

3.2 Content Validity

In order to determine the relevant domainsand completeness of the measures required, ref-erence was made to the wide range of literature inthis field. The areas of life suggested to impact onHR-QOL in ESRD are as follows:� freedom/control/independence[15,16]� social relationships,[15] including family rela-

tionships[16,17]

� anxiety[15,18]

� role,[15,17] including work[19]

� energy[15,16,19]

� body image[15,16]

� sexual relations[15,16]

� mental attitude/mood[15,16]

� sleep[15,19,20]

� cognitive function[15]

� finances[16,17,19]

� recreation and exercise[16]

� relationships with medical staff[15]

� patient education[15]

� physical symptoms[17,19]

� physical function[17,19]

� pain[19,20]

� general dialysis issues[15] (specifically for dialysis)

22 Glover et al.


� dietary restrictions[15,17] (specifically for dialysis)� scheduling of dialysis sessions[15] and time re-

strictions[17,18] (specifically for dialysis).Based on our review of the literature, we

drafted a conceptual framework of the aspects oflife on which ESRD impacts (figure 1).

4. Generic Instruments Usedto Measure QOL

Of the six generic measures (see table I), fourcan be said to measure health status rather thanHR-QOL, while the remaining two measure gen-eral QOL. The instruments most used (accordingto our literature search) were the Medical Out-comes 36-Item Short Form Survey (SF-36),[21]

the EuroQOL 5 Dimension (EQ-5D),[22] theWHO QOL assessment (WHOQOL-BREF),[23]

and the Sickness Impact Profile (SIP).[24]

The tool most commonly used to study HR-QOL in people with renal disease is the SF-36.[21]

This tool has been used to study HR-QOL inmany different chronic disease populations. Itconsists of 36 questions that form eight healthsub-scales: physical functioning, social function-ing, physical role limitations, emotional rolelimitations, bodily pain, mental health, vitality,and general health perceptions. An overall scorecan be obtained from the SF-36 and the scorecan also be broken down into two sub-scores:physical and mental component summaries. TheSF-36 has been translated into a number of dif-ferent languages and is now the most frequently

used generic health status instrument across theworld.[5] It should be noted, however, that theSF-36 is a measurement of health status and notHR-QOL.

The SF-36 has been used to study HR-QOLacross all different treatment modalities in renaldisease. The HR-QOL between treatment mo-dalities has been compared in numerous studiesusing the SF-36. Although there have been manystudies using the SF-36 to compare the HR-QOLbetween hemodialysis and CAPD patients, resultshave varied. A meta-analysis found no differ-ence in the HR-QOL between dialysis modal-ities.[25] It could be suggested that the resultsof studies that show a difference in HR-QOL be-tween patients using hemodialysis and those us-ing peritoneal dialysis could be explained by thedifferences in those patients that undertake thedifferent forms of dialysis. Indeed, this suggestionhas been made in a meta-analysis of QOL (notincluding HR-QOL) across different renal re-placement therapies.[26] There is a bias in CAPDprovision towards younger, fitter, and more ca-pable patients.[27]

Studies using the SF-36 have found that renaltransplantation leads to a better HR-QOL thandialysis.[25] The SF-36 has also been used to ex-amine the HR-QOL of caregivers and patientswith renal disease[28] and also the HR-QOL oflive kidney donors.[29,30]

Many studies have also used other measuresalongside the SF-36 to attempt to identify predic-tors of HR-QOL in renal disease. One example

HR-QOL Control/independence

Mental attitude/mood Recreation

Pain

Cognitive function

Family relationshipsEnergy

Social relationships

Time

Finances

Physical symptoms/health

Sleep

Physical function

Sex life

Work

Body image

Dietary restrictions

Fig. 1. Draft framework of health-related quality-of-life (HR-QOL) measurement in end-stage renal disease (ESRD), i.e. the aspects of life onwhich ESRD can impact.



being that poor sleep quality, depression, andclinical measurements such as low serum albuminlevels have been associated with lower HR-QOLin CAPD patients.[31]

The efficacy of different medical treatmentshas been studied in ESRD using the SF-36. Ina study measuring the difference in HR-QOL inrelation to different immunosuppressant drugs,the SF-36 showed no difference, whereas thedisease-specific ESRD Symptom Checklist(ESRD-SCL) showed a significant improvementin scores between different immunosuppressivemedications.[32] This highlights the limitations ofusing a generic measurement to assess HR-QOLin ESRD.

The SF-36, although widely used in this pop-ulation, does not cover issues regarding sleep,family relationships, issues of control and in-dependence, sexual problems, body image, cog-nitive function, finances, or treatment-specificissues, all of which have been shown to be im-portant in the ESRD population.[4]

The EQ-5D[22] is a generic measure of healthstatus that has been used with the intention ofmeasuring HR-QOL. It can be self-administeredor administered by proxy and is a brief measureof current health status. The EQ-5D consists offive dimensions (mobility, self-care, usual activ-ities, pain/discomfort, and anxiety/depression)and a visual analogue scale. This has been used in

an ESRD population alongside other HR-QOLmeasures to show a higher HR-QOL for trans-plant than for dialysis patients[33] and also hasshown no difference in HR-QOL between thedialysis modalities.[34] The EQ-5D has also showna relationship between dialysis adequacy andHR-QOL.[35] The EQ-5D asks about activitiesnot relationships, which in itself excludes a largearea that has been shown to be important in anESRD population.[36] Other areas that are ex-cluded are treatment-specific issues, sleep, sex,cognitive function, body image, and finances.

TheWHOQOL-BREF[23] was developed fromthe 100-item WHOQOL and consists of 26 items.It was developed in order to assess individuals’perceptions of their QOL. As well as providingan overall QOL score, it provides scores on fourspecific domains: physical health, psychologi-cal, social relationships, and environment. TheWHOQOL BREF, used alongside the SF-36,showed an increase in HR-QOL scores for kidneydonors compared with a similar cohort of non-donors.[37] The WHOQOL-BREF also showed adecrease in HR-QOL for hemodialysis patientsover time that was not present for CAPD pa-tients.[38] The HR-QOL for transplant recipientswas found, again, to be higher than that of thoseon dialysis.[39] Table II shows that the WHOQOL-BREF actually covers most of the issues importantto the ESRD population, except treatment-specific

Table I. Generic measures used in end-stage renal disease health-related quality of life (QOL) research

Instrument Items Brief Description

Medical Outcomes Study Short

Form 36 (SF-36)

36 Items are grouped into eight domains: physical functioning, bodily pain, mental health,

energy/vitality, general health perception, physical role limitations, emotional role limitations,

and social functioning

EuroQOL 5 Dimension (EQ-5D) 5 Provides a simple descriptive profile of self-care, mobility, usual activity, pain,

anxiety/depression, and a visual analog scale

Sickness Impact Profile (SIP) 136 Measures every-day activities in 12 categories (sleep and rest, emotional behavior, body care

and movement, home management, mobility, social interaction, ambulation, alertness,

communication, work, recreation, and eating

Nottingham Health Profile (NHP) 38 Used to evaluate perceived distress across various populations. It consists of six dimensions:

physical mobility, pain, social isolation, emotional reactions, sleep, and energy

WHO QOL assessment

(WHOQOL-BREF)

26 Includes two items to assess overall QOL and general health, the rest of the items are grouped

into four domains: physical, psychological, social relationships, and environment

Life Satisfaction Index (LSI) 20 Provides a cumulative score of QOL. A modification of the instrument, LSI-Z, has 13 items.

Dimensions include zest for life; resolution and fortitude; congruence between desired and

achieved goals; high physical psychological, and social self-concept; happy, optimistic mood

tone

24 Glover et al.


issues. This is perhaps unsurprising, as theWHOQOL Group see QOL as such a wide andall-encompassing concept. It is unclear why thisinstrument is not used more often with this pop-ulation. One explanationmight be simply that theSF-36 has been seen to be the ‘gold standard’ forso long.

The SIP[24] consists of 136 items and aimsto describe a person’s changes in behavior dueto illness. The SIP measures everyday activities in12 categories (sleep and rest, emotional behavior,body care and movement, home management,mobility, social interaction, ambulation, alert-ness behavior, communication, work, recreationand pastimes, and eating). Scoring can be carriedout at the level of categories and dimensions aswell as at the total SIP level. The SIP has beenused to measure HR-QOL in relation to treat-ment[40,41] and has again shown transplant

patients to have a better QOL than those on di-alysis.[42] The ESRD studies that have used theSIP tomeasure QOL are generally older, with oneof the most recent published in 2000.[40] As such,it may be safe to assume that the SIP has fallenout of favor in this population perhaps because ofthe availability of other shorter measures.

Generic measures of HR-QOL are useful inthe renal domain in many ways. Using generictools such as the SF-36means that patients can becompared with population norms in many dif-ferent countries. Generic measurements also en-able researchers to study HR-QOL in the broaderrenal field such as with donors and caregivers.Generic instruments such as the EQ-5D can beused in cost-utility analysis to establish the costeffectiveness of treatments. Generic measures allowa comparison of disease burden and they can alsobe used to look at the QOL of individuals. Generic

Table II. Content validity of patient-reported outcome instruments used in the assessment of health-related quality of life (HR-QOL) in end-

stage renal disease (ESRD)

Aspect of life Generic instruments ERSD-specific instruments

health status QOL KDQOL-SF KDQ ESRD-SCL QLI

SF-36 EQ-5D SIP NHP LSI WHOQOL-BREF

Control/independence O O O O O O OSocial relationships O O O O O OFamily relationships O O O O O OSleep O O O O O OSex life O O O O O OEnergy O O O O O O O O OCognitive function O O O O OPhysical function O O O O O O O O OPhysical symptoms/health

O O O O O O

Body image O O O O O OPsychological issues O O O O O O O O O OPain O O O O O O O OWork O O O O O O OFinances O O ORecreation/leisure O O O O O O ODialysis-specific aspects

Time issues O ODietary restrictions O OEQ-5D =EuroQOL 5 Dimension; ESRD-SCL =ESRD Symptom Checklist; KDQ =Kidney Disease Questionnaire; KDQOL-SF =KidneyDisease QOL instrument; LSI =Life Satisfaction Index; NHP =Nottingham Health Profile; QLI =Ferrans and Powers QOL Index – dialysis

version; SF-36 =Medical Outcomes 36-Item Short Form Survey; SIP =Sickness Impact Profile; WHOQOL-BREF =WHO QOL assessment.



measures of HR-QOL do not include many of theaspects of life specific to those with ESRD and sotheir suitability in this population is limited.

5. Renal-Specific Instruments

The renal-specific instruments most commonlyused to study QOL are the Kidney Disease QOL(KDQOL),[43] Kidney Disease Questionnaire(KDQ),[44] ESRD-SCL,[45] and Ferrans and Pow-ers QOL Index – Dialysis version (QLI).[46]

The KDQOL in its varying forms (KDQOL,KDQOL-SF, KDQOL-36) has become increas-ingly popular in assessing HR-QOL in ESRD.In the short time it has existed it has been trans-lated into many different languages. The originalKDQOL is based around the SF-36, with addi-tional questions specific to kidney disease con-cerning symptoms/problems, effects of kidneydisease on daily life, burden of kidney disease,cognitive function, work status, sexual function,quality of social interaction, and sleep.[43] It wasdeveloped for use with a dialysis population butit has also been found to be valid and reliable ina kidney transplant population.[47] However, aswith many HR-QOL tools, it was validated incomparison with the SF-36, which, as statedpreviously, is a health status measure and not anHR-QOL measure. Therefore, comparing thevalidity of the KDQOL (or any HR-QOL meas-urement) against the SF-36 can only providelimited, at best, measures of validity. Indeed, asthe KDQOL is based around the SF-36, its val-idity can be brought into question.

Using the KDQOL, it was found that psy-chological factors, including depression, were amuch stronger determinant of QOL than bio-logical measures such as dialysis adequacy.[48]

Table II shows that the KDQOL-SF which con-tains 80 items, covers all of the aspects shownto be important in the ESRD population, beingcomprehensive while not overly long. The origi-nal KDQOL contains 134 items and theKDQOL-36 consists of 36 questions and containsthe SF-12 (but does not include questions oncognitive function, sleep, or finances).

The KDQ[44] contains 26 questions in five di-mensions: physical symptoms, fatigue, depres-

sion, relationships with others, and frustration.The KDQ has been used in identifying how totreat anemic ESRD patients appropriately[49,50]

and has also been used to explore the validity ofusing the SF-36 in a renal population.[51] It hasbeen used to find that HR-QOL in people whowere diagnosed with chronic renal failure earlierwas higher than if it was diagnosed later.[52] Theauthors suggest this is because of the consequentlack of pre-dialysis care.

The ESRD-SCL[45] was developed to assessQOL after renal transplantation, focusing ontransplantation-specific symptoms, side effects ofimmunosuppressive therapy, and psychologicaldistress. The ESRD-SCL consists of 43 items insix dimensions: limited physical capacity, limitedcognitive capacity, cardiac and renal dysfunction,side effects of corticosteroids, increased growthof gum and hair, and transplantation-associatedpsychological distress items. All questions arescored on a 5-point Likert scale. The ESRD-SCLhas already been noted as more sensitive in thetransplant population than the SF-36.[26] It hasbeen shown to demonstrate differences in disease-specific distress, which is suggested to be theresult of intercultural differences in reportingpsychological and disease-specific distress.[53] Ithas also been used alongside the SF-36 to showthat psychological distress whilst on dialysis canlead to long-term lower HR-QOL, even aftertransplant.[54] It should be noted that the ESRD-SCL is used mostly by the authors who developedit. It also has the limitation of being designed fortransplant recipients and no publications usingthe English-language version have been found inthe literature. The ESRD-SCL is predominatelybased on symptoms and physical side effects oftreatments. It does not cover relationships, workor finances, leisure and recreation, sex, or issuesof control. As such, although the symptoms dis-cussed are very relevant to the ESRD population,it does not cover all areas important to this pop-ulation and does not appear to measure QOL asdefined by the WHO.

The QLI[46] consists of 64 items with the inten-tion of measuring QOL in terms of satisfactionwith life. It is actually a generic questionnaire thatwas initially developed using dialysis patients

26 Glover et al.


(with added questions concerning dialysis bring-ing the item number to 68). The dialysis versionof the QLI has been used many times to studyHR-QOL in the ESRD population. The QLIappears to be used alongside other HR-QOLmeasures (including the SIP and Adult Self-Image scales[55,56]) in the renal population. It hasalso been used on its own to show an increasein HR-QOL following a renal rehabilitation ex-ercise program[57] and to compare the HR-QOLof patients with CAPD with that of their spous-es.[58] Looking at table II, the QLI actually seemsto measure many of the aspects important to theESRD population, only omitting the areas ofsleep, cognitive function, and time issues specificto treatment. It is unclear then why this measureis not used more often with this population.

6. Discussion

The use of generic or disease-specific instru-ments depends on the nature and aims of eachindividual study. Disease-specific instruments arepotentially more sensitive to those aspects thatare important in that specific population. Con-sequently, they may be more appropriately usedwhen trying to determine treatment effects.Disease-specific instruments may not be appli-cable to other populations and, if different dis-eases or conditions are to be compared, then ageneric instrument is arguably more suitable.Generic instruments may also be appropriate ifdata are to be compared with population norms,the family members of patients, or indeed donors.The limitation of the generic instruments in thispopulation is that they may be unable to detectsmall clinically significant changes, as has beenshown in a study that used both the SF-36 and theESRD-SCL.[32]

In terms of which generic measure to use forthe ESRD population, the WHOQOL-BREFappears to be the most appropriate in terms of itscontent validity. The SF-36, seen as the ‘goldstandard’ does not cover all of the issues im-portant to the ESRD population and it could beargued that it is used primarily in order to facili-tate comparisons as it has been used in studiesfocusing on a range of other conditions. It is

simple to administer, short, and the results areeasy to compare across different groups but, as itdoes not measure all aspects of the HR-QOL ofthe ESRD population, it is recommended thatcaution is exercised when using the SF-36 withthis population. Instead, the WHOQOL-BREFshould be used, as it has many of the advantagesof the SF-36 and also appears to be more valid tothe ESRD population.

There are, of course, problems in challengingthe status quo, in that the WHOQOL-BREF isnot currently used as widely as the SF-36. Thus,it will be necessary to build a body of evidenceusing the WHOQOL-BREF in order to be ableto make the same comparisons and to performmeta-analyses such as those currently carried outon studies that have used the SF-36. Such adevelopment may be preferable to applying aninstrument that is essentially not valid to thepopulation.

On an individual level, HR-QOL instrumentshave the potential to uncover the issues im-portant to and affecting the individual patient.The co-morbidities and complications involvedin chronic renal disease and ESRD are such thateach individual is truly that. This makes themeasurement of HR-QOL very important to thisgroup in order to treat each patient in the waythat he/she, in his/her unique situation, requires.

If the HR-QOL of each individual is to beexamined, then an instrument must be used thatadequately covers the issues important to the in-dividual with ESRD. The KDQOL-SF appearsto be most valid for this purpose. That is not tosay that the KDQOL-SF covers every aspectimportant to every individual within this popu-lation, but it is an appropriate tool to help pin-point individual problems and difficulties andcan be used as a starting point for further dis-cussion. The KDQOL-SF also appears to be themost appropriate tool that can be used to com-pare groups and treatments within the ESRDpopulation. If the SF-36 is the ‘gold standard’ ofgeneric HR-QOL measures in ESRD, then theKDQOL is fast becoming the ‘gold standard’ ofdisease-specific measures in this population. Asthe KDQOL is based around the SF-36, it issuggested that it is perhaps modified in the future



to include questions relating to another moreappropriate tool such as the WHOQOL. Thismight enable comparison between different disease/condition groups and norms whilst using theKDQOL.

In terms of the HR-QOL of family members,many aspects of HR-QOL that affect patientsalso affect their close families. Therefore, in orderto measure the HR-QOL of this group ade-quately, it could be that a disease-specific ques-tionnaire is adapted to meet their needs and thisshould also be investigated in the future.

The purpose of the current review has been toconduct a comprehensive published empiricalliterature search for instruments used to studyHR-QOL in an ESRD population, although somepapers may have been inadvertently omitted.However, as the aim of this review is to identifythe most commonly used self-administered in-struments in the measurement of HR-QOL in anESRD population, the methods and search termsused were deemed adequate for this purpose.While other instruments exist, those included inthis review have been selected on the basis thatthey are the most frequently used within researchand practice environments.

7. Conclusions

HR-QOL could be viewed in two very differ-ent ways: as QOL in relation to health (such asphysical symptoms) or the impact of health onQOL. If the WHO definitions of health and QOLare to be accepted, then HR-QOL can be definedin very broad terms such as how health impactson the overall QOL of a person. Indeed, whenpatients themselves are asked what is importantto them and on which aspects of their life thedisease impacts, their answers cover much morethan just physical symptoms.[15-18] Therefore, theinstruments used to measure HR-QOL in anESRD population need to measure far more thanjust direct physical or mental domains and coverareas such as relationships and the wider impactson life.

The issue of HR-QOL is very important in theESRD population, particularly because of thehighly individualized nature of the disease. It is of

paramount importance then that the contents ofthe instruments used to measure HR-QOL in thispopulation are valid. The SH-36, the instrumentmost widely used to measure HR-QOL in anESRD population is limited in terms of its con-tent and it is recommended that the WHOQOL-BREF become more widely used when a studycalls for the use of a generic instrument. Whena disease-specific instrument is required, theKDQOL-SF appears to be the most appropriate.Further investigation is needed, however, as theKDQOL-SF is based on the SF-36 and may needto be adapted in order to become a more appro-priate instrument within this context.

Acknowledgments

No sources of funding were used to conduct this study orprepare this review. The authors have no conflicts of interestthat are directly relevant to the content of this review.

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Correspondence: Professor Colin R. Martin, School ofHealth, Nursing and Midwifery, University of the Westof Scotland, Ayr Campus, Beech Grove, Ayr, KA8 0SR,Scotland.E-mail: [email protected]

30 Glover et al.


Understanding and Assessing the Impact of End-Stage Renal Disease on Quality of Life

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