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Keywords:

  • convergent validity;
  • measurement;
  • psychometrics;
  • shared decision-making

Abstract

Background

While there has been a clear move towards shared decision-making (SDM) in the last few years, the measurement of SDM-related constructs remains challenging. There has been a call for further psychometric testing of known scales, especially regarding validity aspects.

Objective

To test convergent validity of the nine-item Shared Decision-Making Questionnaire (SDM-Q-9) by comparing it to the OPTION Scale.

Design

Cross-sectional study.

Setting and participants

Data were collected in outpatient care practices. Patients suffering from chronic diseases and facing a medical decision were included in the study.

Methods

Consultations were evaluated using the OPTION Scale. Patients completed the SDM-Q-9 after the consultation. First, the internal consistency of both scales and the inter-rater reliability of the OPTION Scale were calculated. To analyse the convergent validity of the SDM-Q-9, correlation between the patient (SDM-Q-9) and expert ratings (OPTION Scale) was calculated.

Results

A total of 21 physicians provided analysable data of consultations with 63 patients. Analyses revealed good internal consistency of the SDM-Q-9 and limited internal consistency of the OPTION Scale. Inter-rater reliability of the latter was less than optimal. Association between the total scores of both instruments was weak with a Spearman correlation of r = 0.19 and did not reach statistical significance.

Discussion

By the use of the OPTION Scale convergent validity of the SDM-Q-9 could not be established. Several possible explanations for this result are discussed.

Conclusion

This study shows that the measurement of SDM remains challenging.