Quality of life of caregivers of children with congenital glaucoma: development and validation of a novel questionnaire (CarCGQoL).

PURPOSE

We developed and validated an instrument to measure the quality of life (QoL) of caregivers of children with primary congenital glaucoma (PCG): the Caregiver's Congenital Glaucoma Quality of Life (CarCGQoL) questionnaire.

METHODS

A total of 70 caregivers of children with PCG under follow-up at a tertiary eye care center in India participated in a series of focus groups, and pre- and pilot testing phases in the development of the 45-item CarCGQoL questionnaire. Subsequently, this instrument was administered to 111 caregivers of children with PCG awaiting glaucoma surgery. Response to each item was rated on a four-category scale. Rasch analysis was used to validate the instrument's psychometric properties, such as unidimensionality (by principal components analysis [PCA] of residuals), item fit to model, measurement precision (by person separation [PS]), response category performance, differential item functioning (DIF), and targeting of items to participant's QoL.

RESULTS

Categories required reorganization resulting in a shortened rating scale of 3 categories. The instrument showed misfit to the Rasch model and lacked unidimensionality. Deleting 15 items (obtained through PCA of residuals) restored unidimensionality, but additional items misfit, necessitating item reduction. In addition, 2 items showed DIF and were deleted. Finally, a 20-item CarCGQoL instrument showed good fit and unidimensionality. Targeting was good (0.69 logits) and PS was 2.51, indicating good measurement precision.

CONCLUSIONS

We have developed a psychometrically robust 20-item caregiver derived questionnaire, the CarCGQoL, that is a valid and reliable measure of QoL of caregivers of children with PCG. Given its brevity, it is quick and easy to administer in the clinic, and has potential for use as an outcome measure in clinical trials of treatment of PCG.