Cross-Diagnostic Validity of the Congenital Glaucoma Caregiver's Quality of Life Questionnaire (CarCGQoL).

Abstract

PurposeThe Caregiver's Congenital Glaucoma QoL (CarCGQoL) questionnaire was proposed as a measure of QoL of caregivers with children with primary congenital glaucoma (PCG). Support for its psychometric properties among other diagnostic groups is required for scores to be interpreted in the same manner across groups. Therefore we investigated the measurement properties and cross-diagnostic validity of the CarCGQoL questionnaire among caregivers of children with congenital cataract, retinopathy of prematurity (ROP), and blinding corneal disorders.MethodsEight hundred ninety-one caregivers (mean age, 28.3 years; 76% mothers) of children with congenital cataract (n = 407), ROP (n = 272), and blinding corneal disorders (n = 212) completed the CarCGQoL questionnaire. Rasch analysis was used to investigate the psychometric properties. Unidimensionality (by principal components analysis of residuals, PCA) was examined for each group and for pooled sample. Differential item functioning (DIF) was investigated to explore whether bias in responses to the questionnaire existed for certain subgroups as compared to the reference group (PCG).ResultsAcross groups, six items necessitated removal because of misfit (two common and four uncommon), after which three different versions of the questionnaire emerged. Measurement precision was adequate for each group and for the pooled sample (0.80). Unidimensionality was observed, albeit with some DIF. Regardless of the level of QoL, caregivers in the pooled sample were more likely to endorse two items reflecting ability to face child's disease, and interest to pursue leisure activity, as compared with caregivers of children with PCG.ConclusionsCare must be taken when data from the CarCGQoL questionnaire from different pediatric ocular conditions are pooled, given the presence of DIF between the reference group (PCG) and the pooled sample.Translational RelevanceWhen evaluating the impact of interventions on the caregiver's QoL using the CarCGQoL questionnaire in a pooled sample of pediatric ocular conditions, cross-diagnostic DIF must be taken into account.