Raters Interpret Positively and Negatively Worded Items Similarly in a Quality of Life Instrument for Children: Kid-KINDL

Measurement invariance is an important assumption to meaningfully compare children’s quality of life (QoL) between different raters (eg, children and parents) and across genders. Moreover, QoL instruments may combine using negatively and positively worded items—a common method to reduce response bias. However, the wording effects may have different levels of impact on different raters and genders. Our aim was to investigate the measurement invariance of Kid-KINDL, a commonly used QoL instrument, across genders and raters and to consider the wording effects simultaneously. Third to sixth graders (208 boys and 235 girls) completed the self-rated Kid-KINDL, and 1 parent each of 241 children completed the parent-rated Kid-KINDL. The wording effects were accounted for by correlated traits-uncorrelated methods model. The measurement invariance was examined using multigroup confirmatory factor analysis. Item loadings and item intercepts were invariant across gender and rater when we simultaneously accounted for the wording effects of Kid-KINDL. Our results suggest that Kid-KINDL could be used to compare QoL across gender and that parent-rated Kid-KINDL could be used to measure children’s QoL. Specifically, the invariant factor loadings across child-rated and parent-rated Kid-KINDL suggest that the score weights in each item were the same for both children and parents (ie, the important items identified by the children are the same items identified by the parents). The invariant item intercepts suggest that both children and parents share the same threshold for each item. Based on the results, we tentatively recommend that each score of a parent-rated Kid-KINDL can stand for each child’s QoL.