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Measuring social difficulties in routine patient-centred assessment: a Rasch analysis of the social difficulties inventory

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Abstract

Background Social difficulties may add to the psychological burden experienced by cancer patients. Therefore identifying social difficulties in routine oncology practice may help prevent or alleviate distress. The Social Difficulties Inventory (SDI) is a short questionnaire developed for assessing social difficulties in cancer patients. Although well-validated, not enough is known about the clinical meaning and utility of the instrument or whether the items can be meaningfully summed to form a summary index of “Social Distress”. Purpose To determine, using Rasch analysis, whether the SDI could be used as a summary index of social distress specifically examining three fundamental criteria: item fit, unidimensionality and item invariance. Methods The Partial Credit Model was applied to a heterogeneous sample of cancer patients (n = 609) who had completed the SDI. Results Five items were identified as misfitting (infit mean square ≥ 1.3 and standardised t-statistic ≥ 2) and excluded from the subsequent analysis. The remaining items formed a unidimensional interval scale with no additional factors identified in a principal components analysis of the residuals. No differential item functioning was observed for age, gender, diagnosis, extent of disease or social deprivation. The 16-item SDI can be summed to produce an overall index of social distress, facilitating routine identification of social difficulties. Subsequent work is needed to evaluate whether the instrument is able to identify patients with high levels of social distress requiring intervention.

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Acknowledgements

The authors would like to express their thanks to the patients who completed the questionnaires and interviews, and participated in the focus groups, as well as the team of research assistants who collected the data.

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Authors and Affiliations

  1. Psychosocial Oncology and Clinical Practice Research Group, Cancer Research UK Clinical Centre in Leeds, St James’s University Hospital, Beckett Street, Leeds, LS9 7TF, UK

    Adam B. Smith, Penny Wright, Peter Selby & Galina Velikova

Authors
  1. Adam B. Smith
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  2. Penny Wright
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  3. Peter Selby
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  4. Galina Velikova
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Corresponding author

Correspondence to Adam B. Smith.

Additional information

Peter Selby and Galina Velikova are joint senior authors.

Appendix

Appendix

Appendix 1 Scoring template for the 16-item Social Distress Summary & Individual items
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Smith, A.B., Wright, P., Selby, P. et al. Measuring social difficulties in routine patient-centred assessment: a Rasch analysis of the social difficulties inventory. Qual Life Res 16, 823–831 (2007). https://doi.org/10.1007/s11136-007-9181-9

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  • DOI: https://doi.org/10.1007/s11136-007-9181-9

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