Comparison of the CAT-QoL and PedsQLTM instruments in measuring quality of life in amblyopia treatment: preliminary results

Background/Aims: The Child Amblyopia Treatment Questionnaire (CAT-QoL) is a patient-reported outcome measure (PROM), designed to assess the impact of amblyopia treatment. The aim of this study was to compare the psychometric properties of two PROMs; the CAT-QoL instrument and Pediatric Quality of Life Inventory (PedsQLTM), a generic pediatric PROM. This work was part of a wider project to develop a condition-specific PROM for children with amblyopia. Methods: Three hundred and forty-two participants were recruited in a UK multi-center study. Quality of life data was collected using the CAT-QoL and the PedsQLTM instruments. The psychometric performance of the CAT-QoL and PedsQLTM were examined in terms of acceptability, reliability, and validity. Results: Both instruments demonstrated good reliability (CAT-QoL Cronbach's α = 0.793; PedsQLTMα = 0.872). The convergent validity of the CAT-QoL and PedsQLTM instruments was tested by comparing the instruments to each other. There was a moderate correlation between the PedsQLTM and the CAT-QoL scores, and this relationship was statistically significant (rs = -0.517, p < .000). No statistical significance was found between the level of amblyopia severity and the mean PedsQLTM score (p = .420). Conclusion: It was possible to assess the impact of amblyopia treatment using the CAT-QoL and PedsQLTM instruments. The preliminary findings from this are not conclusive, and it is not possible to advocate the use of one questionnaire over another based upon psychometric performance demonstrated here. This may be due to the sample population, as there were limited numbers of participants with severe amblyopia. Both the CAT-QoL and PedsQLTM instruments were noted to have some issues with ceiling effects at an individual item level. The CAT-QoL and PedsQLTM were reliable (as determined by Cronbach's alpha). The PedsQLTM instrument was not able to discriminate between amblyopia severity groups (discriminant validity). Further research is required to formally assess the psychometric properties of the CAT-QoL questionnaire.