Developing the draft descriptive system for the child amblyopia treatment questionnaire (CAT-Qol): a mixed methods study

Amblyopia is a visual condition that occurs in childhood. Screening programmes exist within the United Kingdom (UK) to detect amblyopia, and once detected treatment is given.

Existing patient reported outcome (PRO) measures for amblyopia do not meet current recommendations for the methods adopted during their development, or the way in which the instruments are administered. The overall aim of this study was to produce a self-complete PRO instrument for amblyopia for children aged 4–7 years that uses children’s responses in the development phase. The study comprised a number of stages. This paper reports on the refinement of the descriptive system for the draft instrument (the Child Amblyopia Treatment Questionnaire, CAT-QoL) using qualitative and quantitative methods.

The study consisted of three components. Children were asked to read, and complete the draft questionnaire as independently as possible. They were then asked about the questionnaire, and its format, in a cognitive debriefing exercise. Observations were made as to the child’s ability to read the questionnaire, particular attention was made as to which individual words participants struggled to read. Children were also asked their opinion on the design layout of the questionnaire. Finally, some children were asked to complete a ranking task to help determine the order of the levels of the items as judged by the children. Mid-rank scoring and statistical level of agreement were calculated for the ranking exercise.

Thirty-two (n=32) participants completed a draft questionnaire; each of these underwent a cognitive de-briefing interview. Twenty-two (n=22) children completed the ranking exercise. Ten children did not understand the concept of ranking. The results of the qualitative phase (cognitive de-briefing interview) were used to modify the wording of items and layout of the instrument. Results of the ranking exercise were used to inform the order of the response levels for the items.

Responses of young children can be used in the development of PRO instruments. They are able to help inform the content, wording, and format of an instrument, ensuring good content and face validity. The results have been used to further refine the CAT-QoL, however further research is required to assess the psychometric properties of the instrument.