Development and validation of the Klinefelter-Associated Neurodevelopmental Difficulties (KAND) Checklist: a three-phase mixed-methods study

Klinefelter syndrome (KS) (47,XXY) is a genetic condition associated with infertility, hormonal imbalances, and a range of neurodevelopmental and psychosocial challenges, including language impairments, executive dysfunction, and difficulties in social functioning. Although these challenges can significantly affect daily life, no uniform terminology or standardized tool currently exists to systematically identify and assess them. Building upon research in tuberous sclerosis complex (TSC) and using the TSC-Associated Neuropsychiatric Disorders (TAND) Checklist as a foundation, this study explored neurodevelopmental difficulties associated with KS and led to the development, initial validation, and translation of the Klinefelter-Associated Neurodevelopmental Difficulties (KAND) Checklist. A three-phase mixed-methods design was used. In Phase 1, a literature review and semi-structured interviews with nine adults with KS and eleven parents identified relevant challenges and informed the preliminary checklist (KAND-PL). In Phase 2, feedback from twenty-four parents and thirteen healthcare professionals, collected through a feedback form and focus group, guided iterative revisions to produce the pre-final version (KAND-PF). In Phase 3, the checklist was evaluated using participant feedback and exploratory psychometric analyses with eighteen individuals with KS and twenty-nine parents. Internal consistency (Cronbach’s α) within conceptually related item groups and correlations with validated behavioral measures (Spearman’s ρ) were examined. Thematic analysis and descriptive statistics were applied to qualitative and quantitative responses. Building on the TAND Checklist, the KAND Checklist addresses KS-specific challenges across 13 domains and a background information section on discussing the diagnosis. Across all phases, input from individuals with KS, parents, and healthcare professionals provided strong evidence for face, content, and response process validity, demonstrating that the checklist covers relevant difficulties, uses clear language, and is feasible for self- and proxy-completion. Internal consistency was good, and preliminary convergent validity was supported through correlations with existing behavioral measures. The KAND Checklist is a reliable, accessible tool for identifying neurodevelopmental difficulties in KS. It is intended to raise awareness, facilitate structured clinical conversations, and encourage individualized care. This study highlights the value of participatory research in developing meaningful tools, promoting holistic care, and fostering collaboration between individuals with KS, their families, and professionals. Further dissemination, translation, and larger-scale validation are needed.