A systematic review of the development and testing of additional dimensions for the EQ-5D descriptive system

ABSTRACT

Introduction: As the five dimensions of the EQ-5D might be insensitive to some populations or conditions, adding one or more specific ‘bolt-on dimensions’, to the EQ-5D may improve its validity and relevance for those groups. Various bolt-on dimensions have been identified and tested the effect on the psychometric performance and utility measurement. Therefore, this systematic review was to review all bolt-on dimensions and report the results of those two effects.

Areas covered: Twelve studies were identified through PubMed, Scopus, and Web of Sciences from inception to January 2019. The bolt-on dimensions generally improved the EQ-5D’s psychometric performance when compared with the standard version. However, evidence is lacking about the impact of bolt-on dimensions on responsiveness, reliability and known-groups validity. Evidence was also mixed for adding a sleep dimension, while interpersonal relationships did not promote a significant improvement on utility measurement.

Expert opinion: Adding bolt-on dimensions could enhance the discriminative power and utility measurement of the EQ-5D; however, careful investigation of the sleep and interpersonal relationships is required since the evidence did not support a significant improvement. Further investigation of the identified bolt-on dimensions on all of the psychometric performance and the incremental utility scores derived from TTO is greatly encouraged.

KEYWORDS:

• EQ-5D
• health-related quality of life
• bolt-on
• psychometric performance
• utility measurement

Article highlights

• As the EQ-5D has only five dimensions, it might be insensitive to some populations or groups of patients.

• Adding one or more dimensions, bolt-on dimension, is expected to improve the validity and responsiveness of the EQ-5D as it may capture some aspects specific to a target population.

• To date, no systematic review has been available to summarize the psychometric performance and effect on utility measurement of a bolt-on dimension.

• Most of the bolt-on dimensions showed a significant improvement in the psychometric performance and utility measurement. However, evidence is lacking about the impact of bolt-on dimensions on the responsiveness, known-groups validity, and reliability.

• Evidence was also mixed for adding a sleep dimension, while IR did not promote a significant improvement in utility measurement. These two dimensions should be further investigated in a larger group of population to confirm the results.

• The development of the value set is justified by the improvement of psychometric performance and effect on utility measurement of the bolt-on dimension.

• This review can pave the way for the future development of a bolt-on version of the EQ-5D questionnaire.

Acknowledgments

We would like to thank the experts for their invaluable opinions on identifying relevant publications to be included in this review. Special thanks also to Mr. Kenneth Paul Martinez and Ms. Gaiyathre Subrain, visiting scholar at Faculty of Pharmaceutical Sciences, Burapha University, for their help in the literature search from three electronic databases.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer Disclosures

A reviewer on this manuscript has disclosed is a member of the EuroQol Group, which develops and manages the use of the instrument. Peer reviewers on this manuscript have no other relevant financial relationships or otherwise to disclose.

Data Availability Statement

The data analyzed and reported in this manuscript is not available for public sharing.

Author contribution statement

All authors were jointly involved in the conception, study design, and coordination. Krittaphas Kangwanrattanakul (KK) was involved in the literature search, review and data extraction, but these processes were rechecked by Wiraphol Pimarn (WP). All authors were involved in drafting and final approval of this manuscript.

Additional information

Funding

This paper was not funded.