Development and Psychometric Validation of the Self‐Care of Cancer Inventory (SC‐CI)

Aim To develop a generic instrument for measuring self-care behaviours in adults with cancer and to evaluate its initial psychometric properties. Design A psychometric validation study was conducted within the ONCO-SHIELD longitudinal observational study at Careggi University Hospital (Florence, Italy) enrolling adult patients with metastatic solid tumours receiving first-line systemic anticancer therapy and an ECOG Performance Status of 0–2. Methods The SC-CI was developed through a theory-driven process including item generation, expert validation, and cognitive interviews, and subsequently evaluated using confirmatory factor analysis, McDonald's omega, test–retest reliability, item response theory, differential item functioning, and convergent validity analyses. Results A total of 305 patients were included (mean age 68.4 years, 68.2% male), mainly with lung (28.2%), lower gastrointestinal (23.3%), and genitourinary cancers (22.0%). Content validity was excellent across domains. Confirmatory factor analysis supported the multidimensional structure of the instrument, with acceptable-to-good fit after minor item refinement. Internal consistency was adequate to good (ω = 0.74–0.85), and test–retest reliability was satisfactory (ICC = 0.70–0.74). Convergent validity was supported by positive correlations with health literacy and by associations of monitoring and management with doctors' health locus of control. Differential item functioning by sex and age was limited and showed negligible practical impact. Conclusion The SC-CI provides promising initial psychometric evidence as a multidimensional, theory-based tool for assessing self-care in patients with metastatic solid tumours receiving systemic anticancer therapy. Implications for the Profession and/or Patient Care SC-CI may support nursing practice by helping identify patients with unmet self-care needs and guide tailored educational and symptom-management interventions in this population. Further validation in independent and more diverse oncology populations is warranted before broader clinical application.