Studies Comparing Numerical Rating Scales, Verbal Rating ... escalas dolor.pdfPain assessment, pain intensity, Numerical Rating Scale, Visual Analogue Scale, Verbal Rating Scale, review

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

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

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


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.

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


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.

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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


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.

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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.

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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


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.

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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


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.


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


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.


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.


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


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


(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.

84. Fayers PM, Hjermstad MJ, Klepstad P, et al. Thedimensionality of pain: palliative and chronic painpatients differ in their reports of pain intensity andinterference. Pain 2011 Mar 31. [Epub ahead ofprint].

85. Stenseth G, Bjørnnes M, Kaasa S, Klepstad P.Can cancer patients assess the influence of painon functions? A randomised, controlled study ofthe pain interference items in the Brief Pain Inven-tory. BMC Palliat Care 2007;6:2.

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

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