Does Inclusion of Interactions Result in Higher Precision of Estimated Health State Values?

Anna Nicolet* (Corresponding Author), Catharina G.M. Groothuis-Oudshoorn, Paul F.M. Krabbe

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

1 Citation (Scopus)
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Background: Most preference-based instruments producing overall values for health states are devised on the simplifying assumption that the overall effect of distinct health-related quality of life domains (attributes) of the instrument equals the sum of the attributes. Nevertheless, health attributes are often inter-related and depend on each other. Objectives: To investigate whether inclusion of second-order interactions in the three-level EuroQol five-dimensional questionnaire (EQ-5D-3L) value function would result in better fit and lead to different health state values than a model with main effects only. Methods: Using an efficient design, 400 pairs of EQ-5D-3L health states were generated in a pairwise choice format. We analyzed responses of 4000 people from the general population using a conditional logit model, and we tested goodness of fit using pseudo R2, Akaike information criterion, differences in log-likelihood, and likelihood ratio. We compared accuracies of models’ predictions based on root mean square error and mean absolute error. Results: The interaction-effects model showed systematically lower values than the main-effects model. Inclusion of interactions resulted only in a slightly better model fit. Interactions comprising mobility and self-care were the most salient. Conclusions: For the EQ-5D-3L, a value function based on interactions produces systematically lower values than a main-effects model, meaning that the effect of two or more health problems combined is stronger than the sum of the individual main effects.

Original languageEnglish
Pages (from-to)1437-1444
Number of pages8
JournalValue in health
Issue number12
Publication statusPublished - Dec 2018


  • EQ-5D-3L
  • Main effects
  • Second-order interactions
  • Values
  • Discrete choice

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