The visual analogue WOMAC 3.0 scale--internal validity and responsiveness of the VAS version

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aut.researcherKersten, Paula
dc.contributor.authorKersten, P
dc.contributor.authorWhite, PJ
dc.contributor.authorTennant, A
dc.date.accessioned2011-11-23T21:49:45Z
dc.date.available2011-11-23T21:49:45Z
dc.date.copyright30 April 2010
dc.date.issued30 April 2010
dc.description.abstractBackground Many people suffer with Osteoarthritis (OA) and subsequent morbidity. Therefore, measuring outcome associated with OA is important. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) has been a widely used patient reported outcome in OA. However, there is relatively little evidence to support the use of the Visual Analogue Scale (VAS) version of the scale. We aimed to explore the internal validity and responsiveness of this VAS version of the WOMAC. Methods Patients with chronic hip or knee pain of mechanical origin, waiting for a hip or knee joint replacement completed the WOMAC as part of a study to investigate the effects of acupuncture and placebo controls. Validity was tested using factor analysis and Rasch analysis, and responsiveness using standardised response means. Results Two hundred and twenty one patients (mean age 66.8, SD 8.29, 58% female) were recruited. Factor and Rasch analysis confirmed unidimensional Pain and Physical Functioning scales, capable of transformation to interval scaling and invariant over time. Some Differential Item Functioning (DIF) was observed, but this cancelled out at the test level. The Stiffness scale fitted the Rasch model but adjustments for DIF could not be made due to the shortness of the scale. Using the interval transformed data, Standardised Response Means were smaller than when using the raw, ordinal data. Conclusions The WOMAC Pain and Physical Functioning subscales satisfied unidimensionality and ordinal scaling tests, and the ability to transform to an interval scale. Some Differential Item Functioning was observed, but this cancelled out at the test level and, by doing so, at the same time removed the disturbance of unidimensionality. The scaling characteristics of sets of items which use VAS require further analysis, as it would appear that they can lead to spurious levels of responsiveness and scale compression because they exaggerate the distortion of the ordinal scale.
dc.identifier.citationBMC Musculoskeletal Disorders 2010, vol. 11 (0), pp.80-91
dc.identifier.doi10.1186/1471-2474-11-80
dc.identifier.issn1471-2474 (print) 1471-2474 (online)
dc.identifier.urihttps://hdl.handle.net/10292/2658
dc.languageeng
dc.publisherBioMed Central
dc.relation.urihttp://dx.doi.org/10.1186/1471-2474-11-80
dc.rights© 2010 Kersten et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
dc.rights.accessrightsOpenAccess
dc.subjectActivities of Daily Living
dc.subjectAcupuncture Analgesia
dc.subjectAged
dc.subjectArthralgia
dc.subjectData Interpretation, Statistical
dc.subjectDisability Evaluation
dc.subjectFemale
dc.subjectGreat Britain
dc.subjectHumans
dc.subjectMale
dc.subjectMiddle Aged
dc.subjectOsteoarthritis, Hip
dc.subjectOsteoarthritis, Knee
dc.subjectOutcome Assessment (Health Care)
dc.subjectPain Measurement
dc.subjectPlacebo Effect
dc.subjectPredictive Value of Tests
dc.subjectReproducibility of Results
dc.titleThe visual analogue WOMAC 3.0 scale--internal validity and responsiveness of the VAS version
dc.typeJournal Article
pubs.organisational-data/AUT
pubs.organisational-data/AUT/Health & Environmental Science
pubs.organisational-data/AUT/PBRF Researchers
pubs.organisational-data/AUT/PBRF Researchers/Health & Environmental Sciences PBRF Researchers
pubs.organisational-data/AUT/PBRF Researchers/Health & Environmental Sciences PBRF Researchers/HES R & O Research
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