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Quality of Life Research

, Volume 20, Issue 4, pp 507–511 | Cite as

Measurement invariance of the 16-item social distress scale

  • Adam B. Smith
  • Penny Wright
  • Peter Selby
  • Galina Velikova
Article

Abstract

Purpose

The SD-16 is a 16-item instrument assessing social distress in cancer patients. In addition to work underlining the scale’s reliability, validity and clinical utility, recent research has also determined minimally important differences (MID) for the instrument. The aim of this study was to assess whether item locations remained stable over time, in order to support the longitudinal use of the instrument.

Methods

Data were collated from cancer patients (N = 123) who had completed the SD-16 at four time points (baseline, 6 months, 1 and 2 years). The Partial Credit Model (Rasch analysis) was applied to the data and item fit evaluated against published criteria. Measurement invariance of item location and person measures over time was assessed using analysis of variance.

Results

Good item fit was found with the exception of one item (“work”), which demonstrated misfit at two time points. No statistically significant differences were found for item locations. As anticipated, there were changes over time in patients’ scores, particularly in the first 6 months.

Conclusions

The instrument can be used longitudinally to accurately assess changes in cancer patients’ social distress.

Keywords

Social distress Rasch Longitudinal Cancer 

Notes

Acknowledgments

The authors wish to express their thanks to the patients who completed the questionnaires, the staff for facilitating the study, and the research assistants who collected the data. This work was supported by a programme grant from Cancer Research UK.

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Copyright information

© Springer Science+Business Media B.V. 2010

Authors and Affiliations

  • Adam B. Smith
    • 1
  • Penny Wright
    • 2
  • Peter Selby
    • 2
  • Galina Velikova
    • 2
  1. 1.Centre for Health & Social Care, Leeds Institute of Health SciencesUniversity of LeedsLeedsUK
  2. 2.Cancer Research—UK Psychosocial and Clinical Practice Research GroupSt. James’s University HospitalLeedsUK

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