School of Health and Related Research, University of Sheffield
Abstract
Background: Caries Impacts and Experiences Questionnaire for Children (CARIES-QC) is a child-centred caries-specific quality of life measure. This study aimed to select, and validate with children, a classification system for a paediatric condition-specific preference-based measure, based on CARIES-QC.
Methods: First, a provisional classification system for a preference-based measure based on CARIES-QC was
developed using Rasch analysis, psychometric testing, involvement of children and parents, and the developer of
CARIES-QC. Second, qualitative, semi-structured ‘think aloud’ validation interviews were undertaken with a
purposive sample of children with dental caries. The interviewer aimed to identify whether items were considered
important and easily understood, whether any were overlapping and if any excluded items should be reintroduced.
Interview recordings were transcribed verbatim and thematic analysis conducted.
Results: Rasch analysis identified poor item spread for the items ‘cross’ and ‘school’. Items relating to eating
were correlated and the better performing items were considered for selection. Children expressed some confusion
regarding the items ‘school’ and ‘food stuck’. Parent representatives thought that impacts surrounding
toothbrushing (‘brushing’) were encompassed by the item ‘hurt’. Five items were selected from CARIES-QC for
inclusion in the provisional classification system; ‘hurt’, ‘annoy’, ‘carefully’, ‘kept awake’ and ‘cried’. Validation
interviews were conducted with 20 children aged 5-16 years old. Participants thought the questionnaire was
straightforward and covered a range of impacts. Children thought an item about certain foods being ‘hard to eat’
was more relevant than one about having to eat more carefully because of their teeth and so the ‘carefully’ item
was replaced with ‘hard to eat’.
Conclusion: Following child-centred modification, the preliminary five-item classification system is considered
valid and suitable for use in a valuation survey. The innovative child-centred methods used to both identify and
validate the classification system can be applied in the development of other preference-based measures