The Social Difficulties Inventory (SDI): development of subscales and scoring guidance for staff

Psychooncology. 2011 Jan;20(1):36-43. doi: 10.1002/pon.1705.


Aims: To develop subscales for clinical use of the Social Difficulties Inventory (SDI) with score interpretation guidance for use in routine oncology practice.

Background: Patient-reported outcome measures are used increasingly in cancer care but successful implementation is dependent on a combination of sound psychometrics, guidance on clinical meaning and good clinical judgement. The SDI, a 21-item instrument (SDI-21) developed for use in cancer care, demonstrated good psychometric properties. Rasch analysis of the SDI resulted in a 16-item interval scale of Social Distress (SD-16), which allowed for establishment of some clinical utility guidance but further work was required to optimise meaningful interpretation in clinical practice.

Data sources: Data were pooled from three studies investigating psychometrics and clinical utility of the SDI-21.

Statistical analyses: Common factor analysis was undertaken on SD-16 items. Subscales were derived from the resulting factors and calculated by summing the scores of associated items. Subscale reliability was evaluated using Cronbach's α.

Results: There were 652 participants. A three-factor model explaining 53.3% of the variance was extracted forming the basis of the subscales: Everyday living, Money matters and Self and others. Subscale reliability was good. In a clinical setting, a 2-point change in subscale score could be interpreted as a clinically meaningful difference.

Conclusion: The development of three subscales and clinically significant difference scores for the SD-16, combined with the previously developed cut-off points, improves the clinical utility of the SDI-21 when assessing social issues in oncology care.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Cross-Sectional Studies
  • Factor Analysis, Statistical
  • Female
  • Humans
  • Interpersonal Relations
  • Male
  • Medical Oncology*
  • Middle Aged
  • Neoplasms / psychology*
  • Outcome Assessment, Health Care
  • Patient-Centered Care
  • Psychiatric Status Rating Scales / standards
  • Psychiatric Status Rating Scales / statistics & numerical data*
  • Psychometrics / instrumentation*
  • Reproducibility of Results
  • Surveys and Questionnaires
  • Young Adult