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Vol. 41 No. 6 June 2011 Journal of Pain and Symptom Management
1073
Review Article
Studies Comparing Numerical Rating Scales,Verbal Rating Scales,
and Visual AnalogueScales for Assessment of Pain Intensity
inAdults: A Systematic Literature ReviewMarianne JensenHjermstad,
PhD, PeterM. Fayers, PhD,Dagny F.Haugen,MD,PhD,Augusto Caraceni,
MD, Geoffrey W. Hanks, DSc (Med), MB, Jon H. Loge, MD, PhD,Robin
Fainsinger, MD, Nina Aass, MD, and Stein Kaasa, MD, PhD,on behalf
of the European Palliative Care Research Collaborative
(EPCRC)Regional Center for Excellence in Palliative Care (M.J.H.,
N.A.), Department of Oncology, Oslo
University Hospital-Ullev�al, Oslo, Norway; European Palliative
Care Research Center (M.J.H.,
P.M.F., D.F.H., J.H.L., S.K.), Department of Cancer Research and
Molecular Medicine, Faculty of
Medicine, Norwegian University of Science and Technology and
Trondheim University Hospital,
Trondheim, Norway; Department of Public Health (P.M.F.),
University of Aberdeen, Scotland, United
Kingdom; Regional Center of Excellence for Palliative Care
(D.F.H.), Western Norway, Haukeland
University Hospital, Bergen, Norway; Palliative Care, Pain
Therapy and Rehabilitation Unit (A.C.),
Fondazione IRCCS, National Cancer Institute, Milan, Italy;
Department of Palliative Medicine
(G.W.H.), Bristol Haematology and Oncology Centre, Bristol,
United Kingdom; National Resource
Centre for Late Effects after Cancer Treatment (J.H.L.), Oslo
University Hospital, Oslo, Norway;
Division of Palliative Care Medicine (R.F.), University of
Alberta, Edmonton, Alberta, Canada;
Faculty of Medicine (N.A.), University of Oslo, Oslo, Norway;
and Palliative Medicine Unit (S.K.),
Department of Oncology, St. Olavs University Hospital,
Trondheim, Norway
Abstract
Context. The use of unidimensional pain scales such as the
Numerical Rating
Scale (NRS), Verbal Rating Scale (VRS), or Visual Analogue Scale
(VAS) isrecommended for assessment of pain intensity (PI). A
literature review of studiesspecifically comparing the NRS, VRS,
and/or VAS for unidimensional self-reportof PI was performed as
part of the work of the European Palliative Care
ResearchCollaborative on pain assessment.
Objectives. To investigate the use and performance of
unidimensional painscales, with specific emphasis on the NRSs.
Methods. A systematic search was performed, including citations
through April2010. All abstracts were evaluated by two persons
according to specified criteria.
Results. Fifty-four of 239 papers were included. Postoperative
PI was mostfrequently studied; six studies were in cancer. Eight
versions of the NRS (NRS-6 toNRS-101) were used in 37 studies; a
total of 41 NRSs were tested. Twenty-fourdifferent descriptors (15
for the NRSs) were used to anchor the extremes. When
Address correspondence to: Marianne Jensen Hjermstad,PhD,
Department of Oncology, Regional Centerfor Excellence in Palliative
Care, Oslo University
Hospital, Ullev�al, P.O. Box 4956, Nydalen, Oslo0424, Norway.
E-mail: [email protected]
Accepted for publication: August 17, 2010.
� 2011 U.S. Cancer Pain Relief CommitteePublished by Elsevier
Inc. All rights reserved.
0885-3924/$ - see front
matterdoi:10.1016/j.jpainsymman.2010.08.016
mailto:[email protected]://dx.doi.org/10.1016/j.jpainsymman.2010.08.016http://dx.doi.org/10.1016/j.jpainsymman.2010.08.016http://dx.doi.org/10.1016/j.jpainsymman.2010.08.016
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1074 Vol. 41 No. 6 June 2011Hjermstad et al.
compared with the VAS and VRS, NRSs had better compliance in 15
of 19 studiesreporting this, and were the recommended tool in 11
studies on the basis ofhigher compliance rates, better
responsiveness and ease of use, and goodapplicability relative to
VAS/VRS. Twenty-nine studies gave no preference. Manystudies showed
wide distributions of NRS scores within each category of the
VRSs.Overall, NRS and VAS scores corresponded, with a few
exceptions of systematicallyhigher VAS scores.
Conclusion. NRSs are applicable for unidimensional assessment of
PI in mostsettings. Whether the variability in anchors and response
options directlyinfluences the numerical scores needs to be
empirically tested. This will aid in thework toward a
consensus-based, standardized measure. J Pain Symptom
Manage2011;41:1073e1093. � 2011 U.S. Cancer Pain Relief Committee.
Published by ElsevierInc. All rights reserved.
Key Words
Pain assessment, pain intensity, Numerical Rating Scale, Visual
Analogue Scale, VerbalRating Scale, review
IntroductionThere is an extensive literature regarding
the use of Numerical Rating Scales (NRSs),Verbal Rating Scales
(VRSs), and Visual Ana-logue Scales (VASs) dating from the
1950s.Nearly all of this literature is from the socialsciences,
notably census and surveys, publicopinion polls, and marketing
research. Twoparticular themes emerge in this literature.The first
is a focus on determining the optimalnumber of response options
when using NRSsor VRSs; the second relates to the comparativevalue
of VASs and NRSs.
In the area of cancer pain assessment, themain emphasis of most
authors has been oncomparing VAS scores, the most common mea-sure
for pain intensity (PI) in cancer research,1,2
to the scores obtained on 10-step or 11-stepNRSs (NRS-10 and
NRS-11, respectively). Fewerpapers seem to focus on comparisons
involvingVRSs. Despite the vast body of papers, few arti-cles
recommend the use of one scale over theother. Furthermore, the use
of terms is oftenambiguous. For the purpose of the present pa-per,
we consistently use the abbreviations andterms outlined in the
Appendix.
Two combined expert surveys/literaturereviews3,4 of cancer pain
assessment agreedabout the top three dimensions to include ina
multidimensional assessment of cancer pain:intensity, temporal
pattern, and treatment-relatedfactors (exacerbation/pain relief).
This is in linewith other reports.2,5e7 The recommendations
from consensus meetings on cancer pain con-clude that PI should
be assessed by unidimen-sional scales.2,5,8 Well-validated
instruments,such as the Brief Pain Inventory9 or theshort-form
McGill Pain Questionnaire,10 arerecommended for more comprehensive
painassessment. At present, there is no consensusconcerning the
terminology for temporal fac-tors/breakthrough pain.11e13
The literature shows that NRSs provide suffi-cient
discriminative power for chronic pain pa-tients to describe their
PI.7 Invariably, authorseither report that the NRS and VAS are
equallyefficient for assessment of cancer pain;5 thatthe NRS may be
preferred for assessment ofPI in chronic nonmalignant pain in the
clinicbecause of ease of use and standardized for-mat;7,14 and that
the NRS is preferred by themajority of patients in different
cultures.5,15,16
The European Palliative Care ResearchCollaborative (EPCRC) aims
to design a com-puter-based tool for self-report of frequentcancer
symptoms.17 The first version, primarilyfocusing on pain, was used
in the EPCRC-Computerized Symptom Assessment of pain,depression,
and cachexia, an internationaldata collection study including more
than1000 advanced cancer patients (www.epcrc.org).17 The present
systematic review is onestep of the systematic, iterative process18
to-ward the development of the computerizedtool. We have reviewed
studies with a specifi-cally stated objective of comparing the use
of
http://www.epcrc.orghttp://www.epcrc.org
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Vol. 41 No. 6 June 2011 1075Comparing Scales for Assessment of
Pain Intensity
the NRS, VRS, and/or VAS for unidimensionalself-report of PI, in
cognitively intact adults.Because of the widespread use of the NRS
forthe assessment of PI in many disease groupsand the fact that it
constitutes a major partof more comprehensive assessment tools,
spe-cific focus was put on this scale. The majorstudy aim,
therefore, was to examine the re-sults from comparative studies on
unidimen-sional assessment of PI using the NRS, VRS,or VAS. The
following points were investigated:
� What was the objective of comparing scales,and which scales
were most frequentlycompared?
� Did compliance andusability differ betweenscales?
� Were different modes of scale adminis-tration compared, that
is, plastic rulers,computers?
� Did the number of response options, ver-bal anchor
descriptors, and time framesvary?
� What kind of statistics was used to reportthe results?
� Were patients’ preferences for scalesexamined?
� Did the results from cancer patients differfrom results in
other patient groups?
� Were any of the scales recommended overthe other(s) for
research purposes and/orclinical use, and if so, why?
MethodsThe literature search was performed in the
following databases; MEDLINE (1950e2010,May week 2), PsycINFO
(1806e2010, May week3), and EMBASE (1980e2010 week 20)
throughOvidSP, and the Social ScienceCitation Index inWeb of
Science (1956e2010 update May22) through ISI Web of Knowledge.
Search-term groups representing 1) the NRS/VRS/VAS, 2) evaluation
(including assessment andmeasurement), validation, comparison,
clinime-try (including the clinimetric filter forPubMed/MEDLINE of
Terwee et al.19), and 3) pain, wereapplied in all the combinations
and adaptationsaccording to the specific database and searchengine
requirements. Two limitationsd‘‘adults’’ and ‘‘English’’dwere used.
The de-tailed search profiles can be obtained from thecorresponding
author on request.
All abstracts were read, and papers were se-lected for further
reading if the abstract con-tained any information related to
explicitcomparisons of all or any two of the NRSs,VRSs, and VASs
for assessment of PI. For inclu-sion in the present report, the
publication hadto meet the following criterion: A study witha
specifically stated primary or secondary ob-jective of comparing
NRS/VRS/VAS for self-report of PI in adults.
Thus, case reports, editorials, letters, com-mentaries, reviews,
and overviews were ex-cluded, as were conference abstracts,
andclinical studies simply using different scalesfor PI assessment,
without aiming to comparethe use and properties of scales. Pure
valida-tion studies of new tools or tools translatedfrom the
original language into another alsowere not included. Specific
versions of thescales, that is, Faces Pain Scales (close to
theVRSs) and the box variant with horizontal orvertical boxes for
each value of the NRS,were not included, nor were studies
compar-ing two types of the same scale, for example,the pen and
paper version vs. the plastic ver-sion of the VAS, unless also
comparing themto another scale (NRS/VRS).
In line with the study objectives and becauseof the plethora of
pain assessment tools avail-able, only the NRSs, VRSs, and VASs
used forunidimensional assessment of PI in the in-cluded studies
are described in detail; otherpain tools are listed only in the
tables.
The review process was conducted in twosteps. First, two
independent raters (M. J. H.and I. B.) examined all abstracts
according tothe eligibility criteria, consulting the
full-textpapers if in doubt about inclusion. In cases
ofuncertainty, a third independent classificationwas performed by a
third reviewer (D. F. H.)and subsequently discussed. Second, all
full-text papers of the selected abstracts were readto finally
decide about inclusion. The RelatedArticles function in PubMed and
the referencelists of the included papers were examined
foradditional relevant publications meeting theinclusion
criteria.
ResultsThe searches produced 359 hits (MEDLINE
208, Embase 89, PsycINFO 30, SSCI 32) of
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1076 Vol. 41 No. 6 June 2011Hjermstad et al.
which 120 were duplicates. After screening the239 abstracts, 59
were retained for furtherreading. The main reason for
noninclusionat this stage (69%, 125/180) was that compar-ing scales
for unidimensional assessment of PIwas not a specifically stated
study objective(Fig. 1). Reading of the 59 full-text articles
re-sulted in another 13 papers being excluded,whereas eight
additional papers were identi-fied from the reference lists and/or
the RelatedArticles function. Fifty-four papers were
finallyretained (Fig. 1).
Country of origin showedawide spread: 13pa-pers (24%)were
fromtheUnitedStates, six fromthe United Kingdom, three from
Australia/New Zealand and Canada, respectively, twofrom Africa, one
from Mexico, and one fromChina. The 28 remaining papers were
fromEuropean countries other than the UnitedKingdom, including 12
from the Nordic coun-tries. The majority, 35 (65%), were
publishedin 2000 or later.
Objectives of Comparing Scales and StudySamples
Most of the 54 studies compared differentpain rating scales to
find the most applicablescale for clinical use in a given
population, as
Fig. 1. Flowchart of the literature re
reflected in the samples studied (Table 1). Thir-teen studies
evaluated postoperative PI,20e32
one of these in the elderly.31 Another eightwere conducted in
the emergency room/intensive care unit (ICU).33e40 Six studies
fo-cused on cancer pain,15,41e45 whereas one studyused results from
cancer patients for compari-son.46 Five studies examined pain in
rheuma-toid arthritis.47e51 Four studies evaluated painassessment
in the elderly52e55 in addition tothe one mentioned above.31 Three
were exper-imental studies in volunteers, looking at ratingsof pain
that was inducedby electric orheat/coldstimulations,56e58 whereas
the remaining 14publications59e72 encompassed different
popu-lations and various age spans.Sample size varied from 12 to
1387. In 32
studies, repeated pain assessments were per-formed, in addition
to one study with repeatedassessment in a subsample only for
test-retestpurposes.45 The different scales were pre-sented to the
patients in random order in 25studies (one of which also used fixed
orderin a subsample for test-retest purposes) andin fixed order in
16; the order of presentationwas not specified in 13
studies.Overall, the VASwas by far themost frequently
used scale. A total of 59 VASs were administered
view and selection of papers.
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Table 1Overview of the 54 Studies Comparing Assessments of PI,
Study Objectives, and Conclusions
First Author Study Objectives Population Sample SizeScales for
PIþOther
Scalesa Statisticsb ResultsConclusion and Preference
for Scale Usec
Ahlers, 200833 Compare scales in ICUpatients,
inter-raterreliability, comparescores of observersand patients
Critically illICU
113 NRS-11VAS-100 mm,
rulerþBPS
Kappa coefficients,Spearman rank
High reliability across NRS/VASpatients (0.84). Goodinter-rater
reliability. Observersoften underestimate pain,especially with NRS$
4.
No preference. Self-reportimportant.
Akinpelu,200220
Study relationshipbetween scales,influence ofeducation
WomenCaesareansection
37 VAS-100 mmVRS-11þBox Numerical
Scale
ANOVA, Pearson’s High correlation coefficientsacross scales,
increasing withhigher education.
No preference.
Banos, 198921 Assess the usefulness ofVAS
forpostoperativepain
Postsurgery 212 VAS-100 mmVRS-5
Spearman rank,Pearson’s
High correlation VAS/VRS inpatients. Lower VAS
correlationsbetween patients and observerswith higher pain
levels.
No preference. Nodifferences, VAS valid.
Bergh, 200052 Examine applicabilityof scales in
olderpatients
Geriatric clinic 167 NRS-10VAS-100 mmVRS-7 (GRS)þVerbal
questions
Spearman rank, logisticregression, pair-wisecomparisons
High correlation NRS/VAS/GRS.Lower accomplishment ofscales with
higher age,especially with VAS.
No preference, all scalesuseful, in-depthmeasures necessary
withhigher age.
Bergh, 200153 Compare the verballyreported effect ofanalgesics
withchanges in painscores
Geriatric clinic,nonpathologicalfractures
53 NRS-10VAS-100 mmVRS-7 (GRS)þPRS
As above High correlation NRS/VAS/GRSscales decreasing with
age.Often in contrast with verballyreported analgesic effect.
No preference, all scalesuseful, must besupplemented withscales
for pain relief.
Berthier,199834
Determine the mosteffective method forself-report of acutePI
ER, with/withouttrauma
290 NRS-11VAS-100 mm,
VRS-5, ruler
Pearson’s, t-test, pair-wise comparisons,repeatability
NRS more reliable for traumapatients, equivalent to VASwithout
trauma. NRS/VASbetter discriminant power forall the patients.
NRS preferable due tolower nonresponse rate.
Bolton, 199859 Compare theresponsiveness ofscales
Chiropracticoutpatients
79 NRS-11VAS-100 mmVRS-5
Wilcoxon, Spearmanrank
NRS most responsive for currentpain. For usual
pain,responsiveness of all measureswas enhanced.
NRS preferable due to easeof use. Assessment ofusual pain better
thancurrent pain.
Breivik, 200060 Examine agreement,estimate differencesin
sensitivitybetween scales
Oral surgeryoutpatients
63 NRS-11VAS-100 mmVRS-4
Stochastic simulationtechniques
Large variability in VAS scoreswithin each VRS-4 or
NRS-11category, between patients.Simulations showed VAS wasmore
powerful than VRS.
No preference. Selection ofNRS-11 or VAS to bebased on
subjectivepreferences.
Briggs, 199922 Compare relationshipbetween
scales,examinecharacteristics ofnoncompliantpatients
Orthopedic surgery,secondpostoperativenight
417 VAS-100 mmVRS-5
Spearman rank VAS and VRS scores highlycorrelated, but a wide
rangeof VAS scores correspondingto each VRS category. LowerVAS
completion rate withvarious impairments.
VRS preferred, due tocompliance and ease ofuse.
Brunelli,201045
Compare NRS and VRSfor breakthroughpain exacerbations
Advanced cancerpatients
240 NRS-11VRS-6
Percentage consistentratings, weightedkappa
NRS higher discriminatorycapability between backgroundand peak
PI, lower proportionof inconsistent ratings, higherreproducibility
in PIexacerbations.
NRS preferred, due tohigher discriminatorycapability
andreproducibility.
(Continued)
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Inten
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Table 1Continued
First Author Study Objectives Population Sample SizeScales for
PIþOther
Scalesa Statisticsb ResultsConclusion and Preference
for Scale Usec
Carpenter,199541
Compare pain andmathematicalequivalence,examine nurses’responses
to ratings
Cancer inpatients 50 NRS-6VAS-100 mm
Lower VAS ratings than NRS. >3/4ratings not
mathematicallyequivalent. Nurses provided withfictitious patient
scenarios didnot provide the same painmedication for
equivalentratings.
No preference. Researchinto interpretation ofscales
necessary.
Clark, 200347 Explore patientpreferences forscales,
validation
Rheumatoid arthritisoutpatients
113 VAS-100 mm, rulerVRS-5
Pearson’s, Spearmanrank, c2, ICC
High correlation of scales (>0.79).53% preferred the VRS, 28%
theVAS, 19% had no preference.VRS viewed as easier tounderstand.
Patients with lowereducation (
-
Fauconnier,200937
Compare methods formeasuring pelvic PI
Consecutive sample,gynecologic EU
177 NRS-11VAS-100 mmVRS-5þ2 Nonverbal pain
indexes
Cronbach’s alpha,Pearson’s, factoranalyses, ROC curve
Less missing data for NRS, VRS,and VAS than for the
twobehavioral scales, all methodssensitive to the pain
physiology,location, severity.
No preference.
Ferraz, 199049 Evaluate the reliabilityof three pain scalesin
literate andilliterate patients
Rheumathologyoutpatients
91 NRS-11VAS-100 mmVRS-5
Student’s t-test,Pearson’s, Fisher’s Z
NRS with highest reliability in bothliterate and illiterate
patients,VAS more difficult to complete.
No preference.
Gagliese,200525
Compare feasibilityand validity of scalesfor assessment of
PIacross the adultlifespan
Postoperative pain,older vs. youngerpatients
504 NRS-11VAS-100 mm
horizontaland vertical
VRS-5e
þMc Gill PainQuestionnaire
c2, ANOVA NRS was the preferred scale bypatients, also showed
low errorrates, higher face, convergent,divergent, and criterion
validityregardless of age. VAS difficultin the elderly.
NRS preferred, asproperties were not agerelated.
Grotle, 200461 Compareresponsiveness offunctional and painscales
in the clinicalcourse of disease
Acute and chroniclow back painoutpatients
10450 acute
54 chronic
NRS-11VAS-100 cmþ4 Functional
scales
K-S Lillefors, Student’st-test, standardizedresponse means,ROC
effect size
Both NRS and VAS appropriate,NRS significantly moreresponsive
than VAS in thechronic pain group.
NRS preferred for chronicback pain, but both NRSand VAS
valid.
Heikkinen,200526
Explore congruency ofpatients’ and nurses’ratings, evaluate
useof a pain tool in therecovery room
Postoperative pain 45 NRS-11VAS-100 mmþVerbal
assessment
Spearman rank,Pearson’s, multipleregression analyses
Patients’ ability to use differenttools varied.
Assessmentscorrelated with each other andwith nurses’ estimations.
Nursesboth underestimated andoverestimated patients’ pain.Patients’
verbal pain assessmentsvaried widely.
No preference, not totallyclear whether pain toolsare usable in
therecovery room; furtherresearch necessary.
Herr, 199354 Determine relationshipamong measures,examine the
abilityto use tools correctly,determine toolpreferences
Elderly with legpain
Phase 1: 49Phase 2: 31
VAS-100 mmVRS-6e
NRS-20VAS-100 mm
horizontaland vertical
þPainthermometer
Spearman Brown,Tukey’s post hoc,ANOVA
Phase 1: Higher correlationbetween tools when using sameverbal
anchors; Phase 2: VDSpreferred overall, but hadhigher failure
rates. VAS verticalpreferred to VAS horizontal. Alltools
appropriate.
VAS may be preferred inresearch due to bettersensitivity.
Patients’preferences importantin the clinic.
Herr, 200456 Determine thepsychometricproperties of 5 painscales
in older andyounger adults,examine preferences
Young and oldvolunteers, quasi-experimental(thermal stimuli)
175 NRS-21VNS-11f
VAS-100 mmvertical
VRS-11þFPS
Factor analyses,Cronbach’s alpha,Pearson’s, c2,ANOVA
All scales psychometrically sound,effective in
discriminatingdifferent levels of pain. VDS wasmost sensitive and
reliable inolder. Low failure rates, exceptfor the VAS. NRS
preferred bypatients.
VDS preferred, due topsychometric propertiesand
patients’preference.
Herr, 200750 Evaluate sensitivity andutility of scales inyounger
and older
Rheumathologypatients, quasi-experimental
61 NRS-21VNRS-11f
VAS-100 mmþFPS, IPT
RR of failure torespond, c2, Poissonregression, GLMmethod for
scalesensitivity
The IPT lowest failure rate, highestfor the VNS and the
VAS.Cognitive impairmentsignificantly related to failure onVAS/NRS.
All scales sensitive forPI changes. IPT, followed by theFPS most
preferred by patients.
IPT preferred.
(Continued)
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Inten
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Table 1Continued
First Author Study Objectives Population Sample SizeScales for
PIþOther
Scalesa Statisticsb ResultsConclusion and Preference
for Scale Usec
Holdgate,200338
Test agreementbetween pain scales,calculate minimumclinically
significantchange
Convenience samplewith acute pain, ED
79 VNRS-11VAS-100 mm, rulerþVRS-4 pain relief
Mann-Whitney,Wilcoxon, Spearmanrank, multipleregression
The VAS and VNRS highlycorrelated, but cannot be
usedinterchangeably. Largedifferences between VNRS/VASin paired
observations,significantly higher scores onthe VNRS.
No preference, VNRSuseful.
Huber, 200746 Determine if sensory oraffective
paindimensionspredictedunidimensional PIscores
General cancer, acutepostoperative
pain,chronicmusculoskeletalpain, females
109 NRS-6VAS-100 mmþMAPS
Student’s t-test,MANOVA, Fisher’sZ, Pearson’s,multiple
regression
Unidimensional PI scores mainlyreflect sensory pain
dimensions,supporting the discriminantvalidity of the
NRS/VAS.Separate scales should be usedto rate PI and emotions.
No preference.
Jensen, 198662 Compare PI measureson selected criteria;correct
response,relationship betweenscores
Chronic pain 75 NRS-101VAS-100 mmVRS-4VRS-5þBehavioralRating
Scale(BRS-6)þ Box-11
c2, correlationcoefficients,principal factoranalyses
High correlation across scales,similar rate of correct
responsesand utility, similar predictivevalidity. NRS easier to use
andoffers more response options.
NRS-101 may be preferredbased on ease of use,sensitivity,
andapplicability across agegroup. All scales useful.
Jensen, 200227 Compare the relativesensitivity of threeoutcome
measuresand one compositemeasure for painrelief in two RCTs
Postoperative pain 247 VAS-100 mmVRS-4þVRS relief
ANOVA, F scores Variability in the sensitivity of thepain
ratings, VAS better thanVRS. Pain relief was related yetdistinct
from changes in PI. Thecomposite score did not increasethe
sensitivity of the painassessment.
No preference, choice tobe based on the specificdimension that
relates totreatment.
Jones, 200755 Examine theequivalency of painratings
Nursing homeresidents
135þ 135validationsample
NRS-11VRS-4e
þFPS
Agreement percent,linear regression
Pain levels highly correlated, lowerpain scores reported on the
FPS,greater agreement with amodified FPS.
No preference.
Kenny, 200657 Explore if peopleassign similar levelsof numerical
PI toverbal descriptors
Volunteers 207 VAS-100 mmVRS-15, selfranked
c2, correlations High-correlation VRS/VAS, butrespondents were
idiosyncraticin the use of pain words/descriptors.
No preference. Pain scalesshould supplement
paindescriptions.
Kunst, 199628 Compare pain ratingson VRS and VAS in adiamorphine
study
Postoperative pain,lower abdominalgastrointestinalsurgery
22 VAS-100 mmVRS-5
Variance/covariancemodels used forordinal and intervaldata
VAS/VRS conveyed broadly similarinformation, however, VAS
inindividual patients varied aboutthe patients’ median.
No preference.
Langley, 198451 Investigate relationshipbetween scales
andsensitivity to change
Rheumatology patients 37 VAS-21 cmVRS-7
Pearson’s, Wilcoxon Significant linear relationship, butbetter
approximated by a curve.VAS better than VRS to detect PIchanges,
but warrants furtherinvestigations.
No preference.
Larroy, 200263 Compare scales forassessment ofmenstrual pain
Healthy women 1387 NRS-11VAS-100 mm
Spearman rank Both scales useful, highcorrelation.
NRS preferred due to easeof use andinterpretation.
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Lasheen,200944
Evaluate fluctuation ofsymptoms, comparesymptom scales
Cancer, hospiceinpatients
125 VAS-100 mmVRS-4
c2, ANOVA, regressionanalyses
Significant differences betweenVRS categories andcorresponding
VAS scores, butoverlap too wide to accuratelyassign cut-off points.
VAS lessreliable.
VRS may be better due tolarge variability of VAS.
Li, 200729 Determine thepsychometricproperties andapplicability
of scalesin China
Postoperative pain 173 NRS-11VAS-100 mmVRS-6e
þFPS revised
Spearman rank, ICC,ANOVA, McNemar,Bonferronicorrections
All four scales with goodreliability/validity, highcorrelation,
good sensitivity, alluseful.
FPS preferred.
Loos, 200830 Evaluate the optimaltool after herniarepair
Postoperative pain,outpatients
706 VAS-100 mmVRS-4
Pair-wise comparisons,kappa coefficients
Higher failure rates with VAS, notinfluenced by age.
OverlappingVAS scores within each VRScategory.
VRS preferred due to lowerfailure rates.
Lund, 200564 Evaluate the quality ofthe intraindividualpain
assessment andthe equivalency ofscale cut-offs
Musculoskeletal pain,outpatients
80 VAS-100 mmVRS-5
Pair-wise comparisons,coefficient ofmonotonicagreement
VAS/VRS not to be usedinterchangeably, low intrascaleagreement,
the meaning of therated PI dependent on painetiology.
Probableunderestimation of PI when theVAS was
categorized.Overlapping VAS scores withineach VRS category.
VRS may be preferred, butpain etiology should beconsidered.
Lundeberg,200165
Evaluate theintraindividualdisagreement inpain ratings
Chronic pain patients 69 NRS-21VAS-100 mmþPain matcher
for magnitudematching
Rank-order agreementcoefficient, ROCcurve
All tools reliable and responsive topain relief, only
randomdisagreement, Pain matcher maybe useful.
No preference.
Magbagbeola,200166
Compare and validatepain measures inNigeria
Patients referred tophysiotherapy forpainful conditions
100 VAS-10 cmVRS-4VRS-5
Correlationcoefficients
High correlation across scales,regardless of education. VAS/VRS
can be used together with agood pain history.
No preference.
Marquie,200839
Investigate the use andcorrelation of twopain scales in
Frenchpatients
Emergency inpatientswith pain
198 VNRS-11VAS-100 mm
Pearson’s, Bland-Altman agreement
VAS/VNRS ratings highlycorrelated both for patients
andphysicians, VNRS recommendedas the tool of choice in ED
acutepain.
VNRS preferred due toease of use.
Paice, 199715 Investigate use andvalidity of VNRS-11in
cancer
Convenience sample,cancer pain
50 VNRS-11VAS-100 mmVRS-5g
c2, Mann-Whitney,Spearman rank
High correlation of scales, lowercompliance with VAS
regardlessof age, gender. VNRS preferredby patients.
VNRS preferred due toease of use.
Pesonen,200831
Investigate feasibility oftools for assessmentof acute
postsurgicalpain in elderly
Elderly inpatients withacute pain aftercardiac surgery
160 VAS-100 mmVRS-5þFPS-7, RWS
Student’s t-test,Cochran, Fisher’sexact, Spearmanrank
Lower compliance on VAS andFPS. Pain assessment mostreliable
with VRS and RWS. VAS,FPS not ideal in patients> 75years.
VRS preferred in theelderly, VAS unsuitable.
Peters, 200767 Study the psychometricproperties andpatients’
preferences
Chronic painoutpatients
338 VAS-100 mmhorizontaland vertical
VRS-6e
þBox-11, Box-21
Factor analyses,multilevel logisticregression analyses,logistic
regression
All scales valid, but more mistakeswith increasing age, most on
theVAS. Box scales most preferred,the VDS in the older. In
mixedpopulation, box scale is themethod of choice.
Box-21 preferred.
(Continued)
Vol.
41No.
6June2011
1081
Com
paringScales
forAssessm
entof
Pain
Inten
sity
-
Table 1Continued
First Author Study Objectives Population Sample SizeScales for
PIþOther
Scalesa Statisticsb ResultsConclusion and Preference
for Scale Usec
Price, 199468 Examine and comparescale characteristicsand ease
of use
Orofacial pain andchronic painoutpatients
33 NRS-11VAS-100 mm
horizontal andvertical
M-VAS-100 mm,ruler(mechanical)
Triangulation method,regression, Pearson’s
High correlation between NRS/VAS/M-VAS, all can be used forPI
assessment. Only M-VASprovides ratio scalemeasurement.
M-VAS may be preferreddue to ease of use.Needs
furtherinvestigation.
Rodriguez,200443
Compare theeffectiveness of 3tools forpostoperative painin older
adults
H&N cancer patients,$55 years old,
withcommunicationimpairment
35 NRS-11VAS-100 mmþ FPS
MANOVA High correlation between tools, allappropriate in this
population.NRS the preferred scale, VAS theleast preferred.
NRS may be preferredbased on patients’ andnurses’ views,
butindividual needs to beconsidered.
Seymour,198232
Examine sensitivity andreproducibility ofscales, related
toanalgesic effect
Postoperative painafter dental surgery
12 NRS-11VAS-100 mmVRS-4
Wilcoxon’s High correlation between scales,especially VAS/NRS.
VAS mostsensitive and discriminatedbetter between small changes
inPI.
VAS may be preferred dueto better sensitivity.
Singer, 200140 Compare acute painratings with one-week
recall
Convenience sample ofED patients
50 VNRS-11h
VNRS-101h
VAS-100 mm
Linear regressions,Pearson’s
High correlation between scalesand between initial scores
andrecalled initial pain after oneweek.
No preference.
Skovlund,199569
Compare statisticalpower for treatmentsuccess/failure
Migraine patients, atthe beginning andfour hours aftermedication
in acuteattack
268 VAS-100 mmVRS-4
Stochastic simulationmodel, Wilcoxon’s,C2 test with
Yatsdistribution
Similar reliability and power of VASand VRS, both scales
useful.
No preference.
Skovlund,200570
Compare the sensitivityof two common painscales
Healthy individualswith pain fromendoscopicscreening
168 VAS-100 mmVRS-4
c2, Student’s t-test,stochastic simulationmodel,
two-samplemethod, Wilcoxon’s
VAS consistently more sensitive. VAS may be preferred inmild to
moderate pain,in people with noimpairment.
Svensson200071
PI, scale concordance,statistical modelingfor research
Long-term undefinedpain, prior to bodyawareness course
43 NRS-7VAS-100 mm
Statistical modeling ofdistributions ofpaired
assessments(details in paper)
A certain point on the VAS did notrelate to a numerically
labeledPI on the NRS. ContinuousVAS/NRS offer a falseimpression of
reliable measuresexpressed in millimeters ornumerals.
VRS with clearly describedresponse categoriespreferred for
research.
Williams,200072
Examine patients’ use,description, andinterpretation
Chronic paininpatients þvolunteersample
78 NRS-11NRS-20NRS-101VAS-100 mmþInterviews
Descriptive statisticsonly
Anchor point seemed to affect use,ratings incorporate
variousdimensions of pain; a range ofinternal/external factors,
notonly PI.
No preference.
1082
Vol.
41No.
6June2011
Hjerm
stadetal.
-
Yaku
t,20
0358
Assessreliab
ilityan
dvalidityofthreepain
scales
Volunteers,
experim
entalpain
inducedbytrigge
rpressure
51NRS-11
VAS-10
0mm
VAS-10
0mm
reverse(R
VAS)
Studen
t’st-test,IC
C,
SEM,Pearson’s
Nodifference
inreliab
ilitybetween
RVASan
dVAS,
equally
efficien
t.RVASslightlybetterwithhigh
pain.Rep
licationin
patients
necessary.
Nopreference.
ANOVA¼an
alysis
ofvarian
ce;PI¼pain
intensity;IC
U¼Intensive
Care
Unit;ED¼em
erge
ncy
dep
artm
ent;
ER¼em
erge
ncy
room;Box
Numerical
Scale¼10
vertical
boxe
s,nopain,worst
pain;
ICC¼intraclass
correlationco
efficien
t;BPS¼Beh
avioralPainScale;
GRS¼Graphic
RatingScale;
PRS¼PainReliefScale;
IPS¼Integrated
PainScore;PRI¼PainRatingIndex
;IR
S¼PainReliefScale;
DSS
T¼DigitSymbolSu
bstitutionTest;FPS¼Faces
PainScale;
IPT¼IowaPainThermometer;MAPS¼Multidim
ensional
Affectan
dPainSu
rvey;RWS¼Red
Wed
geScale;
MANOVA¼multivariate
analysis
ofvarian
ce.
aTofacilitate
read
ing;
VAS-10
cman
dVAS-10
0mm
aredescribed
asVAS-10
0mm,regardless
ofthedescriptionin
theactual
pap
er.
b Traditional
descriptive
statistics;mean,percent,med
ian,etc.
arenotlisted
.c D
etailspresentedfortheNRS/
VRS/
VASscales
only.
dVRSnam
edVPSin
pap
er.
e VRSnam
edVDSin
pap
er.
f VNRScalled
VNSin
pap
er.
g VRSnam
edSD
Sin
pap
er.
hCalledNRS-10
andNRS-10
0in
pap
er.
Vol. 41 No. 6 June 2011 1083Comparing Scales for Assessment of
Pain Intensity
in 52 of the 54 studies, relative to 39 VRSs in 37studies.
Insevenstudies, 25,42,48,54,56,67,68averticalversion of the VAS was
used, together with thetraditional horizontal VAS in four of
these.Traditional NRSs were included in 32 studies(33 NRSs),
whereas the verbal version, theVNRS (see Appendix), was used in
another five(eight VNRSs), plus in two of those that alsoused the
NRS,50,56 yielding a total of 41 NRSscales.
The NRSs/VNRSs were compared with theVAS in 16 studies, with the
VRS in two, andwith both the VAS and VRS in 18 studies; theVAS and
VRS were compared in the remaining18 studies. As indicated in Table
1, severalother assessment tools for pain or other symp-toms also
were included in some studies.
The nomenclature used by authors was con-sistent for the
NRSs/VNRSs, with one excep-tion: the acronym VNS used for a VNRS
inone paper. Full consistency was found for theVAS scales, although
specific acronyms wereused for the plastic or mechanical
devicessubstituting for the traditional paper VAS insome studies.
For the VRS scales however,four different abbreviations were used;
VerbalPain Scale, Verbal Descriptor Scale, Simple De-scriptor
Scale, and Graphic Rating Scale. Someof these variants had a number
connected toeach verbal descriptor. For consistency, Table1 uses
only the standard terms NRS, VRS,and VAS.
Compliance and UsabilityWhen reported, better compliance was
re-
ported for the NRSs/VRSs relative to the otherscales in 15
studies, whereas 16 studies did notprovide any such information.
Lower compli-ance on the VAS was found in nine studies, as-sociated
with higher age, degree of trauma, orother impairments. Compliance
results werebased on the number of patients who wereable to perform
the ratings, the number of cor-rect answers, and error rates
percentages. Insome studies, test/retest scores and discrimi-nant
validity between patient groups alsowere used to indicate
compliance.
Different Modes of AdministrationSix studies used a plastic or
mechanical VAS
version with a moveable cursor along a line,with anchors at the
extremes only, as a substi-tute for the traditional paper
VAS.33e35,38,47,68
-
1084 Vol. 41 No. 6 June 2011Hjermstad et al.
Four of these studies were performed in theemergency room or
with ICU patients. Thetwo studies using both the paper and the
rulerversion35,68 concluded that the two versionscorrelated highly,
and that the mechanical ver-sion seemed easier and more practical
in theemergency room when compared with theVNRS.35 The experimental
study of inducedpain/unpleasantness68 used a mechanicalVAS that
also provided an option for judgmentof ratios of perceived PI,
which was regarded asa feasible method for research and
clinicalwork.
One study compared the intraindividual var-iation in repeated
scores on traditional tools(NRS/VAS) with electric skin stimulation
asthe matching stimulus,65 and concluded thatnone of the methods
demonstrated systematicdisagreement. None of the identified
studiesaimed to compare electronic or web-based ap-pliances
(handheld devices, laptop computers,cell phones, etc.) with
traditional paper andpencil versions for PI assessment.
Response Options, Anchor Descriptors, andTime Frames
The NRS-11/VNRS-11 was most frequentlyused (n¼ 26), but six
other versions alsowere used: NRS-6,41,46 NRS-7,71 NRS-10,52,53
NRS-20,54 NRS-21,50,56,65,72 and NRS-101.36,40,62,72 One study38
allowed the patientsto give their score as half integers on
theVNRS-11, which may then be regarded asa 21-point scale. One
study used two NRSs(0e10 and 0e100) that were erroneously la-beled
as NRS-10 and NRS-100,40 whereas oneNRS-101 was used as a
VNRS.36
Five different versions of VRS answer cate-gories were used; 12
used a VRS with four re-sponse categories (VRS-4), 15 used a
VRS-5,seven used a VRS-6, three used a VRS-7, andone used a VRS-11;
one study used a 15-categoryversion57 where the patients were asked
toassign their own verbal descriptors to thenumbers between the two
anchors ‘‘none’’and ‘‘severe.’’ All studies using VAS scalesused
the VAS-100 mm version, also labeled asVAS-10 cm.
As shown in Table 2, the descriptors used forthe extremes
varied, with 24 different adjec-tives being used. ‘‘No Pain’’ and
‘‘Worst PainImaginable’’ were most frequently used; theterminology
was not given in five studies.
Twenty-two studies used the same verbal an-chors for all scales
being compared (threescales or more in nine studies, two scales
in13 studies), and 14 studies used different de-scriptors for all
scales being compared. Amongthe studies that used the same labels
for two ofthree or more scales, the VRSs were most oftenlabeled
differently.The exact wording of the probe questions
that were used for PI assessment was not re-ported in all
papers, nor were the time spansbeing covered. However, 36 studies
specificallyasked for ‘‘current pain,’’ ‘‘present pain,’’ or‘‘pain
right now,’’ supplemented in seven stud-ies with specified ratings
of weakest, worst/strongest, recalled, anticipated, or averagepain
over different periods of time. Anotherseven papers did not specify
the wording, butit was deduced from the objectives and
patientsamples that current pain was being evaluated.Other formats
were PI at rest and when mov-ing/coughing (2); maximal pain last
hour(1); worst pain ever experienced (1); and aver-age pain last
week (3), last 24 hours (2), lastnight (1), and last month (1). One
study sup-plemented the 24-hour PI rating with a ratingof the most
severe PI in the last 24 hours tospecifically address pain
exacerbations.45
Use of StatisticsDescriptive statistics were used in all the
studies (not tabulated). Apart from the statisti-cal modeling
papers that used stochastic simu-lation techniques and other
advancedstatistics, the majority of studies used variousforms of
correlation statistics for comparingscale scores, inter-rater
reliability, and evalua-tion of treatment effect, depending on
pri-mary study outcomes. However, confidenceintervals for the
differences between scaleswere rarely presented and intraclass
correla-tion coefficients were used in five papersonly. Most papers
reported good correlationbetween scales (Table 1), particularly so
be-tween the NRS and VAS. In cases of discrep-ancy, the NRS scores
were higher than theequivalent VAS scores, particularly so for
theverbal NRSs.38 One study found that morethan 75% of the patients
provided ratingsthat were not mathematically equivalent onNRS and
VAS.41
Some studies reported a marked variationbetween numerical and
verbal scales, but in
-
Table 2Overview of Anchor Labels Used with the NRS/VNRS, VAS,
and VRS
Wording of Anchor Labels
NRS/VRNS VRS VAS
37 Studies 37 Studies 52 Studies
41 Scales 39 Scales 59 Scales
n n n
No pain, worst pain 1 3 5No pain, worst pain possible 2 d 3No
pain, (the)a worst possible pain 3 3 8No pain, worst pain
imaginable 6 3 11No pain, worst pain ever 1 1 3No pain, pain cannot
be worse d d 1No pain, worst pain experienced d 1 dNo pain (at
all),a unbearable pain 4 4 5No pain, pain as bad as it could be 4 d
4No pain, very intense pain d d 1No pain, the most intense pain
imaginable 3 1 4No (pain) (at all),a (severe) pain 2 10 3No pain
(at all),a very severe pain d 2 dNo pain (at all),a the most severe
pain possible d 1 dNo pain, pain, which could not be more severe d
1 dNo pain, the most severe pain you can possibly imagine 1 d 1No
pain sensation, the most intense pain sensation imaginable 1 d 3No
pain, maximum pain 4 d 3No pain, maximal amount of pain 3 d dNo
pain, intolerable pain 1 d dNo pain, excruciating pain d 5 dMild,
excruciating pain d 1 dNo pain, horrible pain d 1 dLeast possible
pain, worst possible pain d d 1Wording not specified in paper 4 1
3
aIndicates that the words in brackets were used in some tools,
not in others.
Vol. 41 No. 6 June 2011 1085Comparing Scales for Assessment of
Pain Intensity
different directions. One study reported thatVAS scores above 30
mm corresponded tomoderate pain or above on the VRS-4,
therebyincluding 85% of those reporting moderatepain,23 yet another
study found that the step-wise change in the VRS did not
correspondto equally large changes on the other scales,36
and multiple studies found that there wasa wide range of VAS and
NRS scores withineach VRS category22,26,44,60,71 or that
patients’own pain descriptors varied widely regardlessof scale
scores.26 Two of the four papers usedstatistical modeling of data
from various pa-tient samples and reported that VASs weremost
sensitive to changes.60,70
Evaluation of Patient PreferencesSix studies examined patients’
preferences
for scales:43,47,54,56,67,72 in rheumatoid arthritis(1),
geriatric (2), chronic pain (2), and cancer(1) patients,
respectively. All studies useda VAS and different VRSs,
supplemented bythe NRS-11, NRS-21, or NRS-101 in three
studies, and by other scales (Table 1). Althoughpatient
preferences reflect the tools beingused and the population under
study, the VRSwas preferred by the less educated47 and
theelderly,54,67 and the NRS was the instrument ofchoice in
anage-mixedpopulation,56 in chronicpain patients,72 and in
head-and-neck cancerpatients.43
Two studies assessed patient preferences fordifferent versions
of the VAS scales. The el-derly preferred the vertical to the
horizontalversion.54 No preference was demonstratedfor the
traditional horizontal VAS over the re-versed version with the ‘‘no
pain’’ on the rightside.58
Studies in Cancer PopulationsSix studies were done in cancer
patients,
five in samples with mixed cancer diagno-ses,15,41,42,44,45 and
one in head-and-neckcancer.43 Four studies used NRSs/VRNSsand VASs,
supplemented by VRSs in two,15,42
a supplementary measure for PI in one,43
-
1086 Vol. 41 No. 6 June 2011Hjermstad et al.
and the Italian McGill Pain Questionnaire formultidimensional
pain assessment, a scale forpain relief, and an integrated PI and
durationmeasure in one.42 One study compared theVAS-100 mm and a
four-point VRS;44 another,the NRS-11 and VRS-6.45
Study objectives were to compare scales forclinical use with
respect to scaling equivalenceof the NRS-6 vs. the VAS-100 mm41 or
the VAS-100 mm vs. the VRS-4,44 to examine the admin-istration of
the verbal NRS in general,15 andin relation to communication
impairment43
(Table 1). One study compared unidimen-sional ratings of PI with
multidimensionalscales, including duration and relief,42 whereasone
study compared NRS and VRS for assess-ment of episodic pain
exacerbation in chroniccancer pain.45
Although correlations across scales werehigh in all studies, the
recommendations foruse in cancer differed. NRS-11 was recom-mended
in three studies based on resultsand ease of use,15 patient
preferences,43 andbetter psychometric properties (lower
incon-sistency, better discriminatory power, and
re-producibility).45 One study found that theNRS-6 yielded lower
within-patient scoresthan the VAS and that the scales should notbe
used interchangeably;41 no specific recom-mendation for either
scale (NRS/VAS/VRS)was given in the study comparing unidimen-sional
and multidimensional scales.42 Onestudy in hospice patients
concluded that theVAS-100 mm showed no superiority over theVRS in
assessing fluctuating symptoms, thatthere were significant
differences betweenVRS categories and corresponding VASscores, and
the VRS was more appropriatefor symptom assessment in those with
ad-vanced disease. On the basis of the few studiesin cancer, it
cannot be concluded that resultsor recommendations differ from
those inother populations.
Study RecommendationsThe majority of papers, 29, did not
conclude
with a preference for one tool over the other(s)(Table 1). Three
papers recommendedtools other than the NRS/VRS/VAS. TheNRS was
considered superior in 11studies,15,25,34,39,43,45,48,59,61e63
primarily be-cause of ease of use and high compliance, al-though
some papers expressed a slight
reservation, claiming that the tool may bebest suited for a
subset of the populationonly. Seven papers recommended using
theVRS22,30,31,44,56,64,71 for ease of use, low age-dependent
failure rates, superior psychometricproperties, and better
responsiveness to fluctu-ating symptoms, although depending on
thepain etiology.64 Four papers recommendedVAS as the preferred
tool, also with some reser-vations.32,54,68,70 Few papers
specifically stated ifthe preference was for clinical use, but
based onthe study objectives, this was likely to be the casein most
papers. Two of the statistical modelingpapers specifically
recommended VRS for re-search.69,71 The arguments were that
althoughthe reliability and power of the VAS and VRSmade them
equally useful for clinical use, thepsychometric properties of the
VRS were betterfor research purposes,69 and that numericalmeasures
such as theNRS/VASprovide false im-pressions of being reliable
measures.71
DiscussionThe level of PI at the initial assessment has
been shown to be a significant predictor ofthe complexity of
cancer pain managementand the time needed to obtain stable pain
con-trol.73 PI is probably the most clinically rele-vant dimension
of the pain experienceregardless of disease. The overarching
impor-tance of this domain was accentuated in thepresent review, in
that 89% of the identifiedstudies were performed in populations
otherthan cancer patients. According to expert sur-veys and
consensus conferences,3e5,8 PI shouldbe assessed by unidimensional
scales based onself-report. The importance of the latter
wasevidenced by the incongruence in some stud-ies between patient
and proxy ratings, withproxies underestimating high pain levels.
De-spite the apparent consensus on PI assessment,our review showed
that PI is monitored bya wide variety of unidimensional scales.
Thedifferences were expressed by the number ofresponse options,
scales of variable lengths,different verbal descriptors, and the
differenttime spans covered. Reviews also have shownthat the
development of new tools for variouspain domains, including
intensity, is a continu-ously ongoing process3 that may further add
tothis variability.
-
Vol. 41 No. 6 June 2011 1087Comparing Scales for Assessment of
Pain Intensity
The objectives in most of the reviewed pa-pers were to find the
most applicable scale inthe population being studied, but only
25papers concluded with a specific recommen-dation. This may be
because the statisticalmethods and sample sizes were insufficient
todetect significant differences. The use of corre-lation
coefficients alone is misleading to de-cide whether one scale
performs better thananother,74 and only a few studies
providedsophisticated statistical methods. This is pre-sumably
because many of the studies were de-signed to test the
applicability of the scaleuse, not psychometric performance. The
latteris supported by the fact that most of the unidi-mensional
scales performed reasonably well inall studies.
Although some studies examined the appli-cability of mechanical,
ruler versions of theVASs, it was a little surprising that none
ofthe identified studies compared computerizedand paper versions of
the different scales. Therapid development in handheld
computertechnology provides ample opportunities forself-report of
symptoms in most settings andalso has been shown as a feasible
assessmentmethod in patients with advanced cancer.75,76
Advanced technology may increase the reliabil-ity of pain and
symptom assessment, facilitatethe transfer of information, and
yield immedi-ate scores that are readily available for clinicalor
research purposes. However, these methodsdo not enhance the
validity and clinical utilityof the assessments per se, which are
dependenton the psychometric properties of the ques-tions that are
being presented to the patients.
The exact number of response options usedin a scale is
important. A scale with only two(e.g., pain/no pain) or three
response op-tions offers little opportunity for discrimina-tion.
Most of the reviewed papers used scaleversions according to current
recommenda-tions, primarily NRS-11s, VRSs up to seven cat-egories,
and VAS-100 mm.2,5,6 An overallconclusion from the general
measurement lit-erature is that there is relatively little gain
inprecision with more than seven options andhardly any above
nine.77,78
The most frequently used scale in the re-viewed studies was the
VAS-100 mm, which isrelatively seldom subject to variations
inlength. This scale potentially offers the great-est opportunities
for discrimination, although
in practice this is illusory if most respondentsare unable to
discriminate PI with precisionbeyond nine or 10 distinct levels.
Only onestudy used a VRS with more than seven points.The NRS-11 has
been shown to perform wellfor PI assessment over the central
portion ofthe continuum (2e8)79 and was the mostused version of the
NRSs. Four studies in thisreview used NRSs ranging from 0 to
100(NRS-101). However, on inspection, thesewere actually presented
as verbal scales, havingthe patient indicate a number between 0
and100 rather than marking the appropriate num-ber. Thus, there
seems to be some ambiguity inrecognizing the scales, calling for
standardiza-tion. It also has been shown that patientstend to treat
the NRS-101 scales as NRS-21 orNRS-11 scales.7 The NRS-11 was the
preferredscale in the few studies investigating patientpreferences
in line with previous reports,77,78
but it should be noted that some VRS-6 scalesmay be scored as
0e2e4e6e8e10, therebycomplying with the preference for the
0e10scales.
As far as we know, no specific recommenda-tions exist with
respect to anchor labels, as evi-denced by the 24 different
descriptors used.Although most scales used ‘‘no pain’’ at thelower
end, there were more variations at theupper extremes (Table 2),
some directly imply-ing a comparison with previous pain
experi-ences (‘‘worst pain experienced’’). One studyconcluded that
the anchor labels incorporateda range of personal values, not only
a descrip-tion of the PI domain.80 Another study by thesame author
showed a lack of concordance be-tween patients and of consistency
within pa-tients when they were completing VASs andNRSs by using
their own descriptions andforced choices.72 In our opinion, it
seemslikely that the labels influence the responses,maybe even more
at the upper end of the scalethan at the lower end, particularly so
in differ-ent languages and cultures. However, to whatextent and in
which direction the actual scoresare influenced, remains an
empirical questionthat needs further investigation.
Nevertheless,standardization with respect to anchor labelsis
warranted and the optimal descriptionshould be aimed for.
The compliance rates were surprisingly highin all studies
reporting this, which may beviewed in context to the different
settings.
-
1088 Vol. 41 No. 6 June 2011Hjermstad et al.
Most papers used the term compliance, re-gardless of the
different statistical or arithme-tic methods used to examine this,
whichactually shows an inconsistent use of concepts,as it covered
both compliance and usability inmost studies.
It is highly likely that responding to a verbalNRS by saying a
number between 0 and 10 orusing a plastic ruler held by a nurse in
theemergency room yields close to 100% compli-ance, whereas
completion of pen and paperscales in elderly cancer patients is
more com-plicated. It also may be that a selection biascomes into
play in these relatively well-controlled studies, with specific
emphasis onprompting as many patients as possible to an-swer.
Overall, however, better compliance wasreported for the NRS
relative to the otherscales, whereas the VAS seemed to be
morecomplicated with higher error rates, especiallyin the elderly
or cognitively impaired, as docu-mented previously.15,81 In
relation to this, itmay be regarded as a study limitation thatour
results were not differentiated betweenstudy populations, for
example, the elderly,the cognitively or physically impaired,
etc.Pain assessment in cognitively impaired adults,however, implies
challenges other than theones related to the actual pain tools and
theircontent, in relation to mode of administration,visual
limitations, layout, print size, actual size,and format of the
paper tool, the need to gothrough the scores with the patient in
moredetail than with the cognitively intact, and soforth. Thus, it
was decided to limit the litera-ture search to those who were
cognitively in-tact, and tabulate specific results from theelderly
in some of the studies as appropriate.
The majority of the reviewed papers showedrelatively consistent
findings with respect tothe correlation between scales, and when
as-sessed, most coefficients between changes inscores over time
were high, indicating thatthe scales tended to measure variations
inthe same direction.45,48 However, several au-thors pointed to the
variation in NRS scoreswithin each bracket of the VRS and
reportedthat ratings were not mathematically equiva-lent, which was
taken as an indication of lowinterchangeability between scales by
someauthors.26,38,45,64
In addition, the expectation of obtainingdirect equivalence
between mathematically
different scales may have been too optimistic.It is probably not
realistic that patients provideequal values on scales with
different layouts, re-sponse options, and anchor labels. The
VRSpain assessment scales that are being consid-ered in this
article have response options cho-sen that are ordinal and
generally assumed tohave approximately equal intervalsdalthoughin
the past this equal-interval assumption hasrarely been tested and
many statisticians wouldargue that ordinal methods of analysis
shouldbe applied.The 54 papers included in the present re-
view constituted only 23% of the papers origi-nally identified
by our search terms. Themajority of the papers that were not
includeddid not have a specific aim to compare scales.Thus, it was
interesting to notice that several ofthese used both NRSs and VASs,
and simply re-ported the mean values to conclude on the ef-ficacy
of analgesic treatment. It may be thatsome of these studies would
have given addi-tional information about the performance ofthe
scales. Despite our thorough reading of ab-stracts and several
articles from treatment stud-ies, it can never be ruled out that we
did notidentify all relevant papers. However, the in-cluded papers
cover a broad spectrum of stud-ies comparing PI assessment tools,
so we donot think that we failed to include importantinformation on
this subject.Another limitation of this study is related to
the heterogeneity of studies, samples, and vari-ety of scales
that may restrict the general rele-vance of our findings.
Additionally, mostpapers based their conclusions and
recom-mendations on descriptive or correlation statis-tics and were
not designed to investigate thepsychometric properties of the
tools, whichmay be fundamentally different in, for exam-ple,
chronic cancer pain vs. acute postopera-tive pain. However, the 11
studies specificallyrecommending the use of NRS were per-formed in
different populations (acute,chronic, or cancer pain) and the
recommen-dations were among others based on feasibilitycriteria,
which are important features both forclinical use and research. The
results from thestudies in cancer patients did not differ fromthe
other studies in any respect. Thus, the het-erogeneity of the
included studies describesvery well this lack of standardization in
PI as-sessment. PI as a dimension is paramount for
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Vol. 41 No. 6 June 2011 1089Comparing Scales for Assessment of
Pain Intensity
all pain management and should follow a stan-dardized assessment
methodology, regardlessof the patient population or whether it isa
part of a multidimensional tool or is usedas an unidimensional
scale.
This means that the same methodology(same scale, wording, time
frame, and format)should be applied when assessing pain overtime in
the same patient population. Some ofthe reviewed studies conclude
that the choiceof scale may depend on factors such as pa-tients’
preferences and/or their level of cogni-tive
functioning.27,47,54,60 We only partly agreeto this. In addition,
it is obvious that certainpopulation characteristics have to be
consid-ered, such as age, frailty, literacy level, and cog-nitive
impairment. For example, the highernumber of errors on the VAS with
increasingage and other impairments makes this scaleless applicable
in the cognitively impaired, asdocumented in the literature.2,5,82
This isalso in line with a recent letter based on a studycomparing
NRS and VRS emphasizing theneed to be selective in the use of
scales for clin-ical use.83 However, because the
psychometricproperties largely depend on certain
basiccharacteristics, the selection of scales is betterguided by
specific consensus-based recommen-dations rather than left to the
judgment of theindividual clinicians. Furthermore, a
standardi-zation and consensus-based recommendationon the use of
scales will facilitate the interpre-tation of results from studies
and make com-parisons across studies possible. It also maybe
necessary to distinguish between PI assess-ments for clinical use
vs. research. We have rea-son to believe that the
recommendationsidentified in the present review were mostly
in-tended for clinical purposes, because onlythree papers
specifically presented recommen-dations for research.
It is important to remember that a complexpain experience
requires a multidimensionalassessment, in line with the general
recom-mendations in cancer.2,5,8 However, directlycombining PI
scores with other measurements,such as pain interference scores,
may be lessrelevant in clinical settings, as it may obscurethe
actual scores of each domain.2,84 Formost clinical purposes, PI is
the key dimensionguiding treatment5 and it has been
questionedwhether cancer patients with multiple symp-toms are able
to discriminate between pain
and other factors that interfere with theirfunctioning.85
Although cancer pain may differ from acute,postoperative, and
chronic pain in many re-spects, the common feature of any pain,
re-gardless of cause, is its subjective nature,which makes it
necessary to assess patients’pain perception in a standardized
manner. Inthis respect, a promising initiative resultedfrom a
consensus meeting on cancer painassessment and classification in
Milan inSeptember 2009.8 In relation to PI, the recom-mendation was
that it should be measured bya 0e10 NRS with the standard endpoints
‘‘nopain’’ and ‘‘pain as bad as you can imagine,’’with clinically
meaningful time frames. Thisconsensus can be supported by the
present re-view. Although the recommendation above wasput forward
for PI assessment in cancer specif-ically, it may well be applied
to other popula-tions as well. Key factors to remember in
thisrespect in relation to the patient populationare level of
cognitive function, which maymake a verbal NRS the instrument of
choice,and the appropriate time frame for monitor-ing changes in PI
over time.8 We think it istime to welcome all consensus-based
ap-proaches that aim to standardize and facilitatethe assessment of
the subjective pain experi-ence to improve pain management and
pro-mote research.
In conclusion, the results show that NRS-11,VRS-7, or VAS all
work quite well. Thus, it isreasonable to say that the most
importantchoice is not the type of scale per se, but theconditions
related to its use, which include:a standardized choice of anchor
descriptors,methods of administration, time frames, infor-mation
related to the use of scales, interpreta-tion of cut-offs and
clinical significance, andthe use of appropriate outcome
measuresand statistics in clinical trials.
We believe that all these areas can be im-proved by an
international consensus processbased on the evidence, which, in our
opinion,should include, at least as a first step, perfect-ing and
standardizing the use of NRS-11.
Disclosures and AcknowledgmentsThe EPCRC is funded by the
European
Commission’s Sixth Framework Programme
-
1090 Vol. 41 No. 6 June 2011Hjermstad et al.
(contract no LSHC-CT-2006-037777) with theoverall aim to improve
treatment of pain, de-pression, and fatigue through translation
re-search. Core scientific group/work packageleaders: Stein Kaasa
(project coordinator),Frank Skorpen, Marianne Jensen Hjermstad,and
Jon H�avard Loge, Norwegian Universityof Science and Technology
(NTNU); GeoffreyHanks, University of Bristol; Augusto Caraceniand
Franco De Conno, Fondazione IRCCSIstituto Nazionale dei Tumori,
Milan; IreneHigginson, King’s College London; FlorianStrasser,
Cantonal Hospital St. Gallen; LukasRadbruch, RWTH Aachen
University; KennethFearon, University of Edinburgh;
HellmutSamonigg, Medical University of Graz; KetilBø, Trollhetta
AS, Norway; Irene Rech-Weichselbraun, Bender MedSystems
GmbH,Austria; Odd Erik Gundersen, Verdande Tech-nology AS, Norway.
Scientific advisory group:Neil Aaronson, The Netherlands Cancer
Insti-tute; Vickie Baracos and Robin Fainsinger,University of
Alberta; Patrick C. Stone, St.George’s University of London; Mari
Lloyd-Williams, University of Liverpool. Project man-agement: Stein
Kaasa, Ola Dale, and Dagny F.Haugen, NTNU.
Authors have no conflicts of interest.Special thanks to
librarian Ingrid Riphagen
at the Medical Library, NTNU, Trondheim, forthe performance of
efficient and precise litera-ture searches, and to Irmelin Bergh
(I. B.) atthe Regional Center for Excellence in PalliativeCare,
OsloUniversity Hospital, for examinationof abstracts.
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Appendi
Descriptions and Abbreviations for NRS,
NRS Numerical rating scale, commonly from 0 to 10 (NRScategories
are labeled, for example, ‘‘No pain at all’’VNS when the scale is
explained or shown on pape
VRS Verbal rating scale. Ordered categorical scale, with
ealevels of PI, ‘‘no pain,’’ ‘‘mild pain,’’ ‘‘moderate painpain
imaginable’’ form a six-category VRS scale (VRSadjectives are
scored by assigning numbers (0e6) to(Verbal Pain Scale), VDS
(Verbal Descriptor Scale),
VAS Visual analogue scale, usually 0e100, a straight line
wimeasured from the ‘‘No pain’’ end to the patient’s mindicating
tens (10, 20, 30, etc.) and sometimes unl
rating scale in cancer patients with pain: a prelimi-nary
report. Support Care Cancer 2009;17:1433e1434.
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2011 Mar 31. [Epub ahead ofprint].
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x
VRS, and VAS Used in the Article
-11) or 1 to 10 (NRS-10). Usually, only the two extremeand
‘‘Worst imaginable pain.’’ NRS may be called a VNRS/r to the
patient, who responds by indicating a number.
ch response option consisting of adjectives. For different,’’
‘‘severe pain,’’ ‘‘extreme pain,’’ and the ‘‘most intense-6). VRS
scales are commonly of lengths four to seven. Theeach response
option. The scale also may be called VPSor SDS (Simple Descriptor
Scale).
th the extreme categories labeled as for NRS. The distanceark is
the VAS score. Usually graduated with labeled marksabeled marks for
the units.
Studies Comparing Numerical Rating Scales, Verbal Rating Scales,
and Visual Analogue Scales for Assessment of Pain Intensit ...
Introduction Methods Results Objectives of Comparing Scales and
Study Samples Compliance and Usability Different Modes of
Administration Response Options, Anchor Descriptors, and Time
Frames Use of Statistics Evaluation of Patient Preferences Studies
in Cancer Populations Study Recommendations
Discussion Disclosures and Acknowledgments References