A cross-cultural adaptation and content validity assessment of the Czech Version Kiddy-KINDL Questionnaire

BACKGROUND: Health-related quality of life (HRQoL) is an important outcome in paediatric research, yet no validated Czech-language instrument exists for preschool children aged 4-6 years. The Kiddy-KINDL questionnaire, covering six HRQoL dimensions in both child self-report and parent proxy-report formats, is a leading candidate for adaptation given its brevity, dual-report design, and cross-cultural breadth. OBJECTIVES: To culturally adapt the KINDL® Children version (4-6 years) and KINDL® Parents version (4-6 years) into Czech, and to assess the content validity of both adapted versions. METHODS: The adaptation followed the 14-stage protocol of the Office of Quality of Life Measures (OQLM), including forward translation, back-translation with iterative OQLM review, and a pre-test with 101 child-parent dyads (children aged 5-6 years) recruited from kindergartens in the Pilsen region. Content validity was assessed by two independent expert panels: an academic expert panel (5 experts, "expert panel" assessment) and a kindergarten teachers panel (10 teachers, "teachers panel" assessment). Items were evaluated using the item-level Content Validity Index (I-CVI), scale-level CVI (S-CVI/A), Aiken's V coefficient, and 95% Wilson score and Penfield-Giacobbi confidence intervals. The pilot interview transcripts were analysed using directed content analysis with a five-category problem-type taxonomy (semantic, idiomatic, experiential, conceptual, observability). RESULTS: Both versions were consistent with pre-specified heuristic validity thresholds across both panels. Expert panel: S-CVI/A = 0.967 (Children) and 0.909 (Parents). Teachers panel: S-CVI/A = 0.900 and 0.941 respectively. All items reached I-CVI ≥ 0.80 following targeted revision; confidence intervals for borderline items were wide, reflecting small panel sizes. Directed content analysis identified three categories of comprehension challenge: semantic ambiguity (Children S2 item 4), observability constraints (Parents S6 item 1; S7 items 11, 12, 14), and experiential challenges (alternating-care home referent; practice item misunderstanding). Two items - Children S2 item 4 and Parents S3 item 4 - met the I-CVI threshold at the teachers panel but retained low Aiken's V values (0.600 and 0.700 respectively). CONCLUSIONS: Both Czech KINDL® versions show validity indices consistent with acceptable content validity and are ready for psychometric validation. The complementary use of Aiken's V alongside I-CVI is recommended as a useful complementary practice that enhances reporting rigour in cross-cultural HRQoL instrument adaptation.