Cargando…

The Visual Analogue WOMAC 3.0 scale - internal validity and responsiveness of the VAS version

BACKGROUND: 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 relative...

Descripción completa

Detalles Bibliográficos
Autores principales: Kersten, Paula, White, Peter J, Tennant, Alan
Formato: Texto
Lenguaje:English
Publicado: BioMed Central 2010
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2874767/
https://www.ncbi.nlm.nih.gov/pubmed/20433732
http://dx.doi.org/10.1186/1471-2474-11-80
_version_ 1782181512193507328
author Kersten, Paula
White, Peter J
Tennant, Alan
author_facet Kersten, Paula
White, Peter J
Tennant, Alan
author_sort Kersten, Paula
collection PubMed
description BACKGROUND: 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. TRIAL NUMBER: UKCRN study ID: 4881 ISRCTN78434638
format Text
id pubmed-2874767
institution National Center for Biotechnology Information
language English
publishDate 2010
publisher BioMed Central
record_format MEDLINE/PubMed
spelling pubmed-28747672010-05-24 The Visual Analogue WOMAC 3.0 scale - internal validity and responsiveness of the VAS version Kersten, Paula White, Peter J Tennant, Alan BMC Musculoskelet Disord Research article BACKGROUND: 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. TRIAL NUMBER: UKCRN study ID: 4881 ISRCTN78434638 BioMed Central 2010-04-30 /pmc/articles/PMC2874767/ /pubmed/20433732 http://dx.doi.org/10.1186/1471-2474-11-80 Text en Copyright ©2010 Kersten et al; licensee BioMed Central Ltd. http://creativecommons.org/licenses/by/2.0 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.
spellingShingle Research article
Kersten, Paula
White, Peter J
Tennant, Alan
The Visual Analogue WOMAC 3.0 scale - internal validity and responsiveness of the VAS version
title The Visual Analogue WOMAC 3.0 scale - internal validity and responsiveness of the VAS version
title_full The Visual Analogue WOMAC 3.0 scale - internal validity and responsiveness of the VAS version
title_fullStr The Visual Analogue WOMAC 3.0 scale - internal validity and responsiveness of the VAS version
title_full_unstemmed The Visual Analogue WOMAC 3.0 scale - internal validity and responsiveness of the VAS version
title_short The Visual Analogue WOMAC 3.0 scale - internal validity and responsiveness of the VAS version
title_sort visual analogue womac 3.0 scale - internal validity and responsiveness of the vas version
topic Research article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2874767/
https://www.ncbi.nlm.nih.gov/pubmed/20433732
http://dx.doi.org/10.1186/1471-2474-11-80
work_keys_str_mv AT kerstenpaula thevisualanaloguewomac30scaleinternalvalidityandresponsivenessofthevasversion
AT whitepeterj thevisualanaloguewomac30scaleinternalvalidityandresponsivenessofthevasversion
AT tennantalan thevisualanaloguewomac30scaleinternalvalidityandresponsivenessofthevasversion
AT kerstenpaula visualanaloguewomac30scaleinternalvalidityandresponsivenessofthevasversion
AT whitepeterj visualanaloguewomac30scaleinternalvalidityandresponsivenessofthevasversion
AT tennantalan visualanaloguewomac30scaleinternalvalidityandresponsivenessofthevasversion