Development and Initial Validation of Quality-of-Life Questionnaires for Intermittent Exotropia

Abstract

The development and initial validation of patient-derived, health-related quality-of-life (HRQOL) questionnaires for intermittent exotropia (IXT). Cross-sectional study. In a development phase, 27 children (age, 2-17 years) with IXT and 1 of their parents. In an initial validation phase, 33 children with IXT and 49 control children (age, 5-17 years), along with 1 parent for each child. Children in the control group had no strabismus or amblyopia. Individual patient interviews generated 35 items for child and proxy (parental assessment of child's HRQOL) questionnaires and 46 items for a parent questionnaire. To reduce to a feasible number of items, questionnaires were administered to 5- to 17-year-old children with IXT (n = 15) and parents of 2- to 17-year-old children with IXT (n = 27). Responses were analyzed using standard item reduction methodology. Three final derived IXT questionnaires (IXTQ): child, proxy, and parent (12, 12, and 17 items, respectively) were administered to children with IXT and control children and to parents of IXT and control children. Likert-type scales ranging from never (100, best HRQOL) to almost always (0, worst HRQOL) were used. Median scores for IXT and control groups, compared using Wilcoxon tests. Median child scores were significantly lower (worse HRQOL) in the IXT group compared with the control group: 85 (quartiles, 73-92) versus 92 (quartiles, 79-96; P = 0.04). Median proxy IXTQ scores were significantly lower for IXT children than controls: 83 (quartiles, 75-94) versus 98 (quartiles, 92-100; P<0.0001). Median parent IXTQ scores also were significantly lower in the IXT group compared with the control group: 68 (quartiles, 56-79) versus 93 (quartiles, 87-99; P<0.0001). A new 3-part patient-derived HRQOL questionnaire for children with IXT and their parents has been developed and validated, comprising child, proxy, and parent questionnaires. These questionnaires detect reduced HRQOL in children with IXT as reported by the children themselves and perceived by their parents (proxy report). Childhood IXT also seems to affect parent HRQOL. The IXTQ HRQOL questionnaires may prove useful in the clinical assessment of IXT and for clinical trials. The author(s) have no proprietary or commercial interest in any materials discussed in this article.