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Measuring ability to assess claims about treatment effects: a latent trait analysis of items from the ‘Claim Evaluation Tools’ database using Rasch modelling
  1. Astrid Austvoll-Dahlgren1,
  2. Øystein Guttersrud2,
  3. Allen Nsangi3,
  4. Daniel Semakula3,
  5. Andrew D Oxman1
  6. on behalf of the IHC Group
  1. 1Norwegian Institute of Public Health, Oslo, Norway
  2. 2Norwegian Centre for Science Education, University of Oslo, Oslo, Norway
  3. 3Makerere University College of Health Sciences, Kampala, Uganda
  1. Correspondence to Dr Astrid Austvoll-Dahlgren; astrid.austvoll-dahlgren{at}


Background The Claim Evaluation Tools database contains multiple-choice items for measuring people’s ability to apply the key concepts they need to know to be able to assess treatment claims. We assessed items from the database using Rasch analysis to develop an outcome measure to be used in two randomised trials in Uganda. Rasch analysis is a form of psychometric testing relying on Item Response Theory. It is a dynamic way of developing outcome measures that are valid and reliable.

Objectives To assess the validity, reliability and responsiveness of 88 items addressing 22 key concepts using Rasch analysis.

Participants We administrated four sets of multiple-choice items in English to 1114 people in Uganda and Norway, of which 685 were children and 429 were adults (including 171 health professionals). We scored all items dichotomously. We explored summary and individual fit statistics using the RUMM2030 analysis package. We used SPSS to perform distractor analysis.

Results Most items conformed well to the Rasch model, but some items needed revision. Overall, the four item sets had satisfactory reliability. We did not identify significant response dependence between any pairs of items and, overall, the magnitude of multidimensionality in the data was acceptable. The items had a high level of difficulty.

Conclusion Most of the items conformed well to the Rasch model’s expectations. Following revision of some items, we concluded that most of the items were suitable for use in an outcome measure for evaluating the ability of children or adults to assess treatment claims.

  • evidence based medicine
  • shared decision making
  • health literacy
  • outcome measurement
  • multiple-choice
  • patient education
  • Rasch analysis

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  • Contributors AA, ØG and AO wrote the protocol, and the IHC Group provided comments to this protocol. The Claim Evaluation Tools were developed by the IHC Group. AA coordinated all of the development and evaluation process with support from AO. DS, AN and KO performed the data collection and data entry from the field testing. ØG and AA prepared the data files for the analysis, and ØG conducted the Rasch analysis. AA authored this manuscript with significant input from the IHC Group.

  • Funding The IHC project is funded by the Research Council of Norway-GLOBVAC project 220603.

  • Competing interests None declared.

  • Ethics approval The research was approved by the Makerere University School of Medicine Research and Ethics Committee and the Uganda National Council for Science and Technology.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement All data are published as part of this study; additional information is available upon request and on our website All items in the Claim Evaluation Tools Database are available upon request for non-commercial use.

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  • Patient-centred medicine
    Astrid Austvoll-Dahlgren Daniel Semakula Allen Nsangi Andrew David Oxman Iain Chalmers Sarah Rosenbaum Øystein Guttersrud The IHC Group Leila Cusack Claire Glenton Tammy Hoffmann Margaret Kaseje Simon Lewin Leah Atieno Marende Angela Morrelli Michael Mugisha Laetitia Nyirazinyoye Kjetil Olsen Matthew Oxman Nelson K Sewamkambo Anne Marie Uwitonze