Translation, cross-cultural adaptation, and psychometric properties of the family impact scale: a COSMIN-based systematic review

The Family Impact Scale (FIS) is a validated caregiver-reported outcome measure that gauges the impact of children’s oral and orofacial conditions on their families. As its use continues to expand across countries and cultures, the quality of its translated versions and their psychometric properties must be rigorously evaluated. This systematic review sought to assess the translations, cross-cultural adaptations and measurement properties of FIS-14 and FIS-8. This review followed PRISMA 2020 guidelines and the COSMIN methodology. PubMed, Scopus, and Embase were searched, with studies being eligible if they translated or adapted the FIS and evaluated at least one psychometric property among caregivers of children aged 6–14 years. Data extraction and quality appraisal were performed independently by two reviewers. Translation and adaptation processes were evaluated using the framework for translation and cultural adaptation process for patient-reported outcomes measures. Psychometric properties and risk of bias were assessed using COSMIN criteria. Fourteen studies met the inclusion criteria, including three studies utilising FIS-8, ten studies utilising the FIS-14 and one study using both versions, covering nine different language adaptations in total. Most studies adhered to core translation and adaptation steps, but key methodological elements, such as reconciliation, cognitive debriefing and proofreading, were frequently inadequately reported. Content validity was frequently rated “doubtful” due to a lack of methodological clarity. The internal consistency of FIS-14 was acceptable (FIS-14: α = 0.79–0.88), but FIS-8 exhibited inconsistent results. Test–retest reliability was generally good (ICC = 0.75–0.96) but often lacked confidence intervals or model specification. Construct validity was supported in most studies. Measurement error and responsiveness were underreported. Structural validity was only assessed in two studies, while cross-cultural and criterion validity were not evaluated in any studies. FIS-14 demonstrates acceptable reliability and construct validity across a diverse range of settings, supporting its use in assessments of oral health-related quality of life. However, substantial methodological gaps persist when it comes to content validation, responsiveness, structural validity and cross-cultural testing. Future adaptations should follow established guidelines and employ robust statistical methods to ensure comparability and interpretability across different populations.