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Differential item functioning (DIF) in the EORTC QLQ-C30: a comparison of baseline, on-treatment and off-treatment data

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Abstract

Introduction Differential item functioning (DIF) analyses can be used to explore translation, cultural, gender or other differences in the performance of quality of life (QoL) instruments. These analyses are commonly performed using “baseline” or pretreatment data. We previously reported DIF analyses to examine the pattern of item responses for translations of the European Organisation for Research and Treatment of Cancer (EORTC) QLQ-C30 QoL instrument, using only data collected prior to cancer treatment. We now compare the consistency of these results with similar analyses of on-treatment and off-treatment assessments and explore whether item relationships differ from those at baseline.

Methods Logistic regression DIF analyses were used to examine the translation of each item in each multi-item scale at the three time points, after controlling for the overall scale score and other covariates. The consistency of results at the three time points was explored.

Results For most EORTC QLQ-C30 subscales, the DIF results were very consistent across the three time points. Results for the Nausea and Vomiting scale varied the most across assessments.

Discussion The results indicated that DIF analyses were stable across each time point and that the same DIF effects were usually found regardless of the treatment status of the respondent.

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Acknowledgements

This work was funded by the EORTC Quality of Life Group, Cancer Research UK and the University of Aberdeen and carried out under the auspices of the EORTC Quality of Life Group.

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Authors and Affiliations

  1. Section of Population Health, Institute of Applied Health Sciences, University of Aberdeen, Polwarth Building, Foresterhill, Aberdeen, AB25 2ZD, UK

    Neil W. Scott & Peter M. Fayers

  2. Department of Cancer Research and Molecular Medicine, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway

    Peter M. Fayers

  3. Division of Psychosocial Research and Epidemiology, Netherlands Cancer Institute, Amsterdam, Netherlands

    Neil K. Aaronson & Chad Gundy

  4. Quality of Life Department, European Organisation for Research and Treatment of Cancer, Headquarters, Brussels, Belgium

    Andrew Bottomley

  5. Division of Medical Oncology, Department of Internal Medicine, University Medical Centre, Utrecht, Netherlands

    Alexander de Graeff

  6. Department of Palliative Medicine, Bispebjerg Hospital, Copenhagen, Denmark

    Mogens Groenvold & Morten A. Petersen

  7. Institute of Public Health, University of Copenhagen, Copenhagen, Denmark

    Mogens Groenvold

  8. Centre for Clinical Studies, University Hospital Regensburg, Regensburg, Germany

    Michael Koller

  9. Department of Medical Psychology, Academic Medical Centre, University of Amsterdam, Amsterdam, Netherlands

    Mirjam A. G. Sprangers

Authors
  1. Neil W. Scott
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  2. Peter M. Fayers
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  3. Neil K. Aaronson
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  4. Andrew Bottomley
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  5. Alexander de Graeff
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  6. Mogens Groenvold
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  7. Chad Gundy
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  8. Michael Koller
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  9. Morten A. Petersen
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  10. Mirjam A. G. Sprangers
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Consortia

The EORTC Quality of Life Group and the Quality of Life Cross-Cultural Meta-Analysis Group

Corresponding author

Correspondence to Peter M. Fayers.

Appendices

Members of the Quality of Life Cross-Cultural Meta-analysis Group

Australia: M King, S Leutenegger, N Spry; Austria: E Greimel, B Holzner; Belgium: A Bottomley, C Coens, K West; Brazil: G de Castro, C de Souza; Canada: A Bezjak, M Whitehead; Denmark: M Groenvold, M Klee, M Petersen; France: A Brédart, T Conroy, C Rodary; Germany: M Berend, B Bestmann, M Koller, O Krauß, T Küchler, B Malchow, R Schwarz, S Singer; Greece: K Mystakidou; Iran: A Montazeri; Italy: C Brunelli, M Tamburini; Japan: T Matsuoka, H Zhao; The Netherlands: N Aaronson, A de Graeff, R de Leeuw, M Muller, M Sprangers; Norway: K Bjordal, E Brenne, M Hjermstad, M Jordhøy, S Kaasa, P Klepstad, S Sundstrøm, F Wisløff; Singapore: YB Cheung, SB Tan, J Thumboo, HB Wong; South Korea: YH Yun; Spain: J Arraras; Sri Lanka: H Jayasekara, L Rajapakse; Sweden: M Ahlner-Elmqvist; Switzerland: P Ballabeni, J Bernhard; Taiwan: W–C Chie; Turkey: U Abacioglu; UK: J Blazeby, J Bruce, A Davies, P Fayers, L Friend, Z Krukowski, T Massett, J Nicklin, J Ramage, N Scott, A Smyth-Cull, T Young; USA: D Cella, D-L Esseltine, C Gotay, I Pagano.

Contributing groups

European Organisation for Research and Treatment of Cancer (EORTC) Brain Group, EORTC Breast Cancer Group, EORTC Chronotherapy Group, EORTC Gastro-Intestinal Group, EORTC Genito-Urinary Group, EORTC Gynaecological Group, EORTC Head and Neck Group, EORTC Leukaemia Group, EORTC Lung Group, EORTC Lymphoma Group, EORTC Melanoma Group, EORTC Quality of Life Group, EORTC Radiotherapy Group, EORTC Soft Tissue Group, National Cancer Institute Grant CA60068, National Cancer Institute of Canada (NCIC) Clinical Trials Group, Nordic Myeloma Study Group, Swiss Group for Clinical Cancer Research (SAKK).

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Scott, N.W., Fayers, P.M., Aaronson, N.K. et al. Differential item functioning (DIF) in the EORTC QLQ-C30: a comparison of baseline, on-treatment and off-treatment data. Qual Life Res 18, 381–388 (2009). https://doi.org/10.1007/s11136-009-9453-7

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