Evaluation of the Intermittent Exotropia Questionnaire Using Rasch Analysis

Abstract

he Intermittent Exotropia Questionnaire (IXTQ) is a patientderived, intermittent exotropia-specific instrument designed to evaluate health-related quality of life (HRQOL) in children with intermittent exotropia and their parents. 1,2 The IXTQ consists of 3 parts: the 12-item child IXTQ (completed by the child to assess the child's HRQOL), the 12-item proxy IXTQ (completed by the parent to assess the child's HRQOL), and the 17-item parent IXTQ (completed by the parent regarding his or her own HRQOL). 1 The child and proxy questionnaires each have a single subscale. The parent questionnaire contains 3 subscales: psychosocial, function, and surgery. The IXTQ is reliable and valid for assessing HRQOL in children with intermittent exotropia. [1][2][3] It is available for download free of charge at http://pedig.jaeb.org/.The IXTQ was originally developed using classical test theory. Rasch analysis may be used to modify and improve existing HRQOL instruments. [4][5][6][7][8][9] In the present study, Rasch analysis was used to refine the existing IXTQ, removing items that do not contribute meaningful information to the instrument and ensuring that response options are properly interpreted. Methods Patient CohortParents gave written informed consent, and children gave written assent when required. The protocol was approved by the institutional review boards of the Mayo Clinic, Jaeb Center for Health Research, and other local sites involved in the study. Data were collected and analyzed in accordance with the Health Insurance Portability and Accountability Act guidelines. The IXTQ was completed by 575 parents of 575 children aged 1 through 16 years with intermittent exotropia at the time of their child's clinic examination, enrolled from May 15, 2008, through July 24, 2013. The 295 children aged 5 years or older completed the age-appropriate child IXTQ. Parents and children completed the IXTQ as part of routine care in the strabismus practice of one of the authors (J.M.H., n = 110) or at the enrollment examination for 1 of 2 ongoing randomized clinical trials being conducted by the Pediatric Eye Disease Investigator Group (NCT 01032603 [n = 69] and NCT 01032330 [n = 396]). Child questionnaires were administered to children aged 5 through 7 years by study personnel. All 8-to 17-year-old child, proxy, and parent questionnaires were self-administered. Patient demographics are reported in eTable 1 in the Supplement. Statistical AnalysisBefore Rasch analysis, items with floor and ceiling effects on the child, proxy, and parent IXTQs were eliminated as described in the eMethods in the Supplement. Rasch analysis was performed on each of the 4 IXTQs using the analytic methods that we have applied previously (eMethods in the Supplement). 9 The performance and structure of the Rasch-IMPORTANCE The Intermittent Exotropia Questionnaire (IXTQ) is a patient, proxy, and parental report of quality of life specific to children with intermittent exotropia. We refine the IXTQ using Rasch analysis to improve reliability and validity.OBSERVATI...

Symptoms in Children with Intermittent Exotropia and Their Impact on Health-Related Quality of Life

“…(Hatt et al, 2010, Leske et al, 2015) The IXTQ consists of 5 components: Child, Proxy, Parent Psychosocial, Parent Function, Parent Surgery (available at: www.pedig.net accessed February 22, 2016). The Child IXTQ consists of 12 questions (Table 2) and is formatted using a 3-point Likert-type scale (‘Not at all’, ‘Sometimes’, ‘A lot’) for 5–7-year olds and a 5-point Likert-type scale (‘Never’, ‘Almost never’, ‘Sometimes’, ‘Often’, ‘Almost always’) for 8–17-year olds.…”

Associations between Health-Related Quality of Life and the Decision to Perform Surgery for Childhood Intermittent Exotropia

“…Each domain was identified as an independent factor during the development of the IXTQ 6 and was retained as such following Rasch analysis. 19 (Questionnaires available online in administrable format with user instructions: www.pedig.net accessed July 22, 2013). Proxy and Parent questionnaires use a 5-point Likert type scale for responses.…”

Patient‐reported outcome measures in amblyopia and strabismus: a systematic review

“…The quality assessment of the IXTQ is shown in Table . Despite holding good classical test theory‐based psychometric properties, the instrument (child and proxy versions) does not demonstrate good measurement precision and unidimensionality, when validated using the Rasch model …”

“…Just four of the amblyopia‐ and/or strabismus‐specific instruments, namely, the IXTQ, CVLS, AS‐20 and A&SQ, have been validated using the Rasch analysis and only the AS‐20 questionnaire demonstrates good psychometric properties . Both the instruments for children, namely, the IXTQ and the CVLS, lack unidimensionality, an important attribute of any valid instrument . A&SQ, the only validated instrument that claims to measure the impact of amblyopia and strabismus, has items which are not specific to amblyopia and falls short of targeting when tested on the isolated amblyopia group and hence, are deemed unsuitable for assessing the impact of amblyopia …”