Skip to main content
SpringerLink
Log in

Scale invariance and longitudinal stability of the Physical Functioning Western Ontario and MacMaster Universities Osteoarthritis Index using the Rasch model

  • Validation Studies
  • Published:
Rheumatology International Aims and scope Submit manuscript

Abstract

The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) measures the quality of life of patients with osteoarthritis (OA), and there is a specific scale for the physical functioning dimension, the short version with seven items WOMAC-pf. This study describes the application of the Rasch model to explore scale invariance and response stability of the WOMAC-pf short version across affected joint and over time. A sample of 884 patients with OA, from 15 hospitals in Spain, completed the WOMAC-pf before surgery (baseline) and at 3, 6 and 12 months post-surgery of hip or knee. The invariance by joint was explored through the differential item functioning (DIF) analysis of the Rasch model using baseline data, and time stability (DIF by time) were evaluated in stack data (each participant is represented four times, one by time point). Mean age of the patients was of 69.13 years (SD 10.01), 59.3% of them were women (n = 524), 59.2% had knee OA (n = 523) and 40.8% hip OA (n = 361). Item “putting on socks” showed DIF by joint and time. Fit to the Rasch model using stack data improved when this item was removed. Good reliability for individual use, local independency and unidimensionality of the models were confirmed. WOMAC-pf 7-item short version was invariant over time and joint when item “putting on socks” was removed. Researchers should carefully evaluate this item as it presents problems in scale invariance and stability, which could affect results when comparing data by joint or when computing change scores.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Fig. 1
Fig. 2

Similar content being viewed by others

References

  1. Bellamy N, Buchanan WW, Goldsmith CH, Campbell J, Stitt LW (1988) Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee. J Rheumatol 15(12):1833–1840

    CAS  PubMed  Google Scholar 

  2. Ryser L, Wright BD, Aeschlimann A, Mariacher-Gehler S, Stucki G (1999) A new look at the Western Ontario and McMaster Universities Osteoarthritis Index using Rasch analysis. Arthritis Care Res Off J Arthritis Health Prof Assoc 12(5):331–335

    Article  CAS  Google Scholar 

  3. Tubach F, Baron G, Falissard B, Logeart I, Dougados M, Bellamy N et al (2005) Using patients’ and rheumatologists’ opinions to specify a short form of the WOMAC function subscale. Ann Rheum Dis 64(1):75–79

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  4. Rothenfluh DA, Reedwisch D, Müller U, Ganz R, Tennant A, Leunig M (2008) Construct validity of a 12-item WOMAC for assessment of femoro-acetabular impingement and osteoarthritis of the hip. Osteoarthritis Cartil 16(9):1032–1038

    Article  CAS  Google Scholar 

  5. Davis AM, Badley EM, Beaton DE, Kopec J, Wright JG, Young NL et al (2003 Nov) Rasch analysis of the Western Ontario McMaster (WOMAC) Osteoarthritis Index: results from community and arthroplasty samples. J Clin Epidemiol 56(11):1076–1083

    Article  CAS  PubMed  Google Scholar 

  6. Bilbao A, Quintana JM, Escobar A, Las Hayas C, Orive M (2011) Validation of a proposed WOMAC short form for patients with hip osteoarthritis. Health Qual Life Outcomes 9(1):75

    Article  PubMed  PubMed Central  Google Scholar 

  7. Rasch G (1960) Probabilistic models for some intelligence and attainment tests. Nielsen and Lydiche, Oxford

    Google Scholar 

  8. Hobart JC, Cano SJ, Zajicek JP, Thompson AJ (2007) Rating scales as outcome measures for clinical trials in neurology: problems, solutions, and recommendations. Lancet Neurol 6(12):1094–1105

    Article  PubMed  Google Scholar 

  9. Tennant A, Conaghan PG (2007) The Rasch measurement model in rheumatology: what is it and why use it? When should it be applied, and what should one look for in a Rasch paper?. Arthritis Rheum 57(8):1358–1362

    Article  PubMed  Google Scholar 

  10. Wolfe F, Kong S (1999) Rasch analysis of the Western Ontario MacMaster Questionnaire (WOMAC) in 2205 patients with osteoarthritis, rheumatoid arthritis, and fibromyalgia. Ann Rheum Dis 58(9):563–568

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  11. Roorda L, Jones C, Waltz M, Lankhorst G, Bouter L, van der Eijken JW et al (2004) Satisfactory cross cultural equivalence of the Dutch WOMAC in patients with hip osteoarthritis waiting for arthroplasty. Ann Rheum Dis 63(1):36–42

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  12. Whitehouse SL, Lingard EA, Katz JN, Learmonth ID (2003) Development and testing of a reduced WOMAC function scale. J Bone Joint Surg Br 85(5):706–711

    CAS  PubMed  Google Scholar 

  13. Escobar A, Vrotsou K, Bilbao A, Quintana JMA, García Pérez L, Herrera-Espiñeira C (2011) Validation of a short form of the function dimension of the WOMAC questionnaire. Gac Sanit 25(6):513–518

    Article  PubMed  Google Scholar 

  14. Pallant JF, Tennant A (2007) An introduction to the Rasch measurement model: an example using the Hospital Anxiety and Depression Scale (HADS). Br J Clin Psychol Br Psychol Soc 46(Pt 1):1–18

    Google Scholar 

  15. Andrich D (2011) Rating scales and Rasch measurement. Expert Rev Pharmacoecon Outcomes Res 11(5):571–585

    Article  PubMed  Google Scholar 

  16. Martinez-Martin P, Forjaz MJ (2012) How to evaluate validation data. In: Rating scales in Parkinson’s disease. Oxford University Press, Oxford, pp 16–41

    Chapter  Google Scholar 

  17. Masters GN (1982) A Rasch model for partial credit scoring. Psychometrika 47(2):149–174

    Article  Google Scholar 

  18. Smith EV Jr (2002) Detecting and evaluating the impact of multidimensionality using item fit statistics and principal component analysis of residuals. J Appl Meas 3(2):205–231

    PubMed  Google Scholar 

  19. Tennant A, Pallant J (2007) DIF matters: a practical approach to test if Differential Item Functioning makes a difference. Rasch Meas Trans 20(4):1082–1084

    Google Scholar 

  20. Mallison T (2011) Rasch analysis of repeated measures. Rasch Meas Trans 251(1):1317

    Google Scholar 

  21. Linacre JM (2001) Category, step and threshold: definitions and disordering. Rasch Meas Trans 15(1):794

    Google Scholar 

  22. Wright B, Panchapakesan N (1969) A procedure for sample-free item analysis. Educ Psychol Meas 29:23–48

    Article  Google Scholar 

  23. Kubinger KD (2009) On designing data-sampling for Rasch model calibrating an achievement test. Psychol Sci Q 51(4):370–384

    Google Scholar 

  24. Andrich D, Sheridan B, Luo G (2010) RUMM2030 (computer software and manual). RUMM Laboratory, Perth

    Google Scholar 

  25. Kersten P, White P, Tennant A (2010) The visual analogue WOMAC 3.0 scale—internal validity and responsiveness of the VAS version. BMC Musculoskelet Disord 11(80):1–11

    Google Scholar 

  26. Holland P (1993) Wainer. Differential Item Functioning, Educational Testing Service. Lawrence Erlbaum Associates, Hillsdale

    Google Scholar 

  27. Cameron IM, Scott NW, Adler M, Reid IC (2014) A comparison of three methods of assessing differential item functioning (DIF) in the Hospital Anxiety Depression Scale: ordinal logistic regression, Rasch analysis and the Mantel chi-square procedure. Qual Life Res Int J Qual Life Asp Treat Care Rehabil 23(10):2883–2888

    Article  Google Scholar 

  28. Crane PK, Gibbons LE, Jolley L, van Belle G (2006) Differential item functioning analysis with ordinal logistic regression techniques. DIFdetect and difwithpar. Med Care 44(11 Suppl 3):S115–S123

    Article  PubMed  Google Scholar 

  29. Hagquist C, Andrich D (2017) Recent advances in analysis of differential item functioning in health research using the Rasch model. Health Qual Life Outcomes 15(1):181

    Article  PubMed  PubMed Central  Google Scholar 

Download references

Funding

The original study was funded as a multi-centre project by Health Research (PI 04/0938, PI 04/0542 and PI 04/2577) and by the Department of Health of Basque Country (200411012).

Author information

Authors and Affiliations

  1. Institute of Economic, Geography and Demography (IEGD), Spanish Scientific Research Council (CSIC) and Research Network on Health Services and Chronicity (REDISSEC), Madrid, Spain

    Alba Ayala

  2. Research Unit, Basurto University Hospital (Osakidetza), REDISSEC, Bilbao, Spain

    Amaia Bilbao

  3. Agency for Health Technology Assessment, Institute of Health Carlos III and REDISSEC, Madrid, Spain

    Sonia Garcia-Perez

  4. Research Unit, Basurto University Hospital (Osakidetza), REDISSEC, Bilbao, Spain

    Antonio Escobar

  5. Epidemiology and Biostatistics Department, National School of Public Health, Institute of Health Carlos III and REDISSEC, Monforte de Lemos 5, 28029, Madrid, Spain

    Maria João Forjaz

Authors
  1. Alba Ayala
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Amaia Bilbao
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Sonia Garcia-Perez
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Antonio Escobar
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Maria João Forjaz
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

All authors were involved in drafting the article and revising it critically for important intellectual content, and all authors approved the final version to be published. AE and AB were involved in the acquisition of data. AA, AB and MJF were involved in the analysis and interpretation of the data. AA, AB, SGP, AE and MJF critically revised the manuscript. All authors were involved in conception and design of the study and take responsibility for the integrity of the work as a whole, from inception to finished article.

Corresponding author

Correspondence to Maria João Forjaz.

Ethics declarations

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. The clinical research ethics committee “Comité Ético de Investigación Clínica (CEIC) de Euskadi” approved the study on May 2005, protocol number PI010938.

Informed consent

Informed consent was obtained from all individual participants included in the study.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Ayala, A., Bilbao, A., Garcia-Perez, S. et al. Scale invariance and longitudinal stability of the Physical Functioning Western Ontario and MacMaster Universities Osteoarthritis Index using the Rasch model. Rheumatol Int 38, 473–479 (2018). https://doi.org/10.1007/s00296-017-3901-4

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s00296-017-3901-4

Keywords

Search

Navigation