Cross-cultural equivalence of the patient- and parent-reported quality of life in short stature youth (QoLISSY) questionnaire.

BACKGROUND: Testing cross-cultural equivalence of patient-reported outcomes requires sufficiently large samples per country, which is difficult to achieve in rare endocrine paediatric conditions. We describe a novel approach to cross-cultural testing of the Quality of Life in Short Stature Youth (QoLISSY) questionnaire in five countries by sequentially taking one country out (TOCO) from the total sample and iteratively comparing the resulting psychometric performance. METHODS: Development of the QoLISSY proceeded from focus group discussions through pilot testing to field testing in 268 short-statured patients and their parents. To explore cross-cultural equivalence, the iterative TOCO technique was used to examine and compare the validity, reliability, and convergence of patient and parent responses on QoLISSY in the field test dataset, and to predict QoLISSY scores from clinical, socio-demographic and psychosocial variables. RESULTS: Validity and reliability indicators were satisfactory for each sample after iteratively omitting one country. Comparisons with the total sample revealed cross-cultural equivalence in internal consistency and construct validity for patients and parents, high inter-rater agreement and a substantial proportion of QoLISSY variance explained by predictors. CONCLUSION: The TOCO technique is a powerful method to overcome problems of country-specific testing of patient-reported outcome instruments. It provides an empirical support to QoLISSY's cross-cultural equivalence and is recommended for future research.

Assessing the quality of life of health-referred children and adolescents with short stature: development and psychometric testing of the QoLISSY instrument.

BACKGROUND: When evaluating the outcomes of treatment in paediatric endocrinology, the health-related quality of life (HrQoL) of the child is to be taken into consideration. Since few self-reported HrQoL instruments exist for children with diagnosed short stature (dSS), the objective of this study was to develop and psychometrically test a targeted HrQoL instrument for use in multinational clinical research. METHODS: The target population were short stature (height<-2 SDS) children and adolescents (age 8-12 and 13-18 years) with a diagnosis of growth hormone deficiency (GHD) or idiopathic short stature (ISS), differing in growth hormone treatment status. Focus group discussions for concept and item generation, piloting of the questionnaire with cognitive debriefing, and instrument field testing with a retest were conducted simultaneously in five countries. After qualitative and preliminary quantitative analyses, psychometric testing of field test data in terms of reliability and validity including confirmatory factor analyses (CFA) was performed. RESULTS: Following item generation from focus group discussions, 124 items were included in a pilot test with a cognitive debriefing exercise providing preliminary feedback on item and domain operating characteristics. A field test with 268 participants showed high internal consistency reliabilities (alpha 0.82-0.95), good correlations with generic measures (up to r=.58), significant known group differences (e.g. in height: F=32, df 244, p<0.001) and an acceptable CFA model fit suggesting construct validity of the three-domain core structure with 22 items, supplemented by three mediator domains with 28 items. CONCLUSIONS: The QoLISSY questionnaire is a promising step forward in assessing the impact of dSS on HrQoL. It is based on items generated from the subjective experience of short stature children referred for endocrine investigation, is validated for use in five languages and it is easy to administer in clinical and research settings.

Parental perception of health-related quality of life in children and adolescents with short stature: literature review and introduction of the parent-reported QoLISSY instrument.

BACKGROUND: Health-related quality of life (HrQoL) of the child diagnosed with short stature is an important outcome to be assessed both from the patient as well as from the parental perspective. The objective of this study was to review the literature on parent-reported HrQoL and to subsequently develop and psychometrically test the parent-reported version of the Quality of Life in Short Stature Youth (QoLISSY) instrument for use in clinical and epidemiologic research. METHODS: A review of the literature on parental assessment of child HrQoL via PUBMED was followed by a psychometric analysis of data collected within the European QoLISSY study, in which 686 eligible parents of short statured children/adolescents (aged 4-18 years) meeting inclusion criteria participated. Patient inclusion criteria were a height below -2 SD, a diagnosis of growth hormone deficiency (GHD) or idiopathic short stature (ISS), and treatment status in terms of receiving or not receiving recombinant human growth hormone therapy. Focus groups eliciting parental HrQoL statements, pilot testing with cognitive debriefing, and a field test in 317 parents with a retest in 148 parents were conducted simultaneously in France, Germany, Spain, Sweden and the UK. The psychometric performance of the parent-reported instrument, developed in parallel to the child/ adolescent self-report version, was assessed using standard tests of reliability and validity. RESULTS: Literature search failed to identify a cross-culturally developed height specific instrument available for both patient self-report and parental observer report. Analysis of the QoLISSY focus group phase conducted separately in children, adolescents and parents yielded 169 items generated from parent focus groups. A cognitive debriefing exercise followed by a pilot test of preliminary psychometric characteristics resulted in deleting poorly performing items. Field testing of the parent-reported version suggested a three-domain core HrQoL structure with 22 items, additional 44 items assessing three mediator domains and two parent specific domains. The parent report version demonstrated good criterion and construct validity as well as internal consistency and test retest reliability. CONCLUSIONS: The QoLISSY parent report questionnaire closes a gap in the simultaneous assessment of parent and child perception of HrQoL in an international context. It is based on items generated from the experience of short statured children, adolescents and their parents and is validated for use in five European languages. It is feasible, relevant for this population, psychometrically sound and is easy to administer in research and clinical settings.