Validity and Reliability of the 9-item Shared Decision Making Questionnaire (SDM-Q-9) in a National Survey in Hungary

Eur J Health Econ. 2019 Jun;20(Suppl 1):43-55. doi: 10.1007/s10198-019-01061-2. Epub 2019 May 20.

Abstract

Background: The nine-item Shared Decision Making Questionnaire (SDM-Q-9) is one of the most frequently applied instruments for assessing patients' involvement in medical decision-making. Our objectives were to develop a Hungarian version of SDM-Q-9, to evaluate its psychometric properties and to compare its performance between primary and specialised care settings.

Methods: In 2019, a sample of adults (n = 537) representative of the Hungarian general population in terms of age, gender and geographic region completed an online survey with respect to a recent health-related decision. Outcome measures included SDM-Q-9 and Control Preferences Scale-post (CPSpost). Item characteristics, internal consistency reliability and the factor structure of SDM-Q-9 were determined.

Results: The overall ceiling and floor effects for SDM-Q-9 total scores were 12.3% and 2.2%, respectively. An excellent internal consistency reliability (Cronbach's alpha 0.925) was demonstrated. Exploratory factor analysis resulted in a one-factor model explaining 63.5% of the variance of SDM-Q-9. A confirmatory factor analysis supported the acceptability of this model. Known-groups validity was confirmed with CPSpost categories; mean SDM-Q-9 total scores were higher in the 'Shared decision' category (72.6) compared to both 'Physician decided' (55.1, p = 0.0002) and 'Patient decided' (57.2, p = 0.0086) categories. In most aspects of validity and reliability, there was no statistically significant difference between primary and specialised care.

Conclusions: The overall good measurement properties of the Hungarian SDM-Q-9 make the questionnaire suitable for use in both primary and specialised care settings. SDM-Q-9 may be useful for health policies targeting the implementation of shared decision-making and aiming to improve efficiency and quality of care in Hungary.

Keywords: Primary care; Psychometrics; SDM-Q-9; Shared decision-making; Specialised care.

MeSH terms

  • Adolescent
  • Adult
  • Age Factors
  • Aged
  • Aged, 80 and over
  • Decision Making, Shared*
  • Factor Analysis, Statistical
  • Female
  • Humans
  • Hungary
  • Male
  • Middle Aged
  • Patient Participation*
  • Physician-Patient Relations
  • Psychometrics
  • Reproducibility of Results
  • Sex Factors
  • Socioeconomic Factors
  • Surveys and Questionnaires / standards*
  • Young Adult