Development and psychometric evaluation of the Nurses’ Perceived Competence in Comprehensive Delirium Care Scale (NPCCDS): a mixed-methods study

Delirium is among the most prevalent and severe neurocognitive disorders in critically ill patients and requires nurses to possess advanced competencies in assessment, monitoring, prevention, and management. Despite the pivotal role of intensive care nurses in delirium care, no comprehensive instrument currently exists to assess nurses’ perceived competence in comprehensive delirium care (NPCCD). Therefore, this study aimed to develop and psychometrically evaluate the Nurses’ Perceived Competence in Comprehensive Delirium Care Scale (NPCCDS) among intensive care unit (ICU) nurses. This sequential exploratory mixed-methods study was conducted in Iran between June 2025 and March 2026. Scale items were generated through an integrative literature review and qualitative interviews with ICU nurses, followed by qualitative content analysis to identify the conceptual domains of NPCCD. Face and content validity were evaluated qualitatively and quantitatively by ICU nurses and expert panels. Exploratory factor analysis (EFA) was conducted among 350 ICU nurses using Principal Axis Factoring (PAF) with Promax rotation. Confirmatory factor analysis (CFA) and measurement invariance across gender were subsequently examined in an independent sample of 350 nurses. Reliability was assessed using Cronbach’s alpha (α), McDonald’s omega (ω), composite reliability (CR), and intraclass correlation coefficient (ICC). Convergent and discriminant validity were evaluated using average variance extracted (AVE) and the Fornell–Larcker criterion. Additionally, Exploratory Graph Analysis (EGA) was used to provide network-based evidence supporting the dimensional structure identified through conventional factor analyses, whereas Random Forest Modeling (RFM) was employed to examine the relative contribution and predictive importance of individual dimensions and items within the overall NPCCDS. The final NPCCDS consisted of 26 items across four factors: Cognitive-Monitoring Competence in Delirium Assessment and Surveillance (CMCDAS), Clinical Analytical Competence in Delirium Risk and Etiology (CACDRE), Clinical Management and Leadership Competence (CMLC), and Operational and Therapeutic Communication Competence (OTCC). The four-factor structure explained 50.56% of the total variance. Sampling adequacy was excellent (KMO = 0.899), and Bartlett’s test of sphericity was statistically significant (χ² = 3644.32, p < 0.001). The first-order model demonstrated an excellent fit to the data, with χ² = 306.85, df = 293, p = 0.277, χ²/df = 1.04, RMSEA = 0.019 (90% CI: 0.001–0.032), CFI = 0.991, TLI = 0.990, and SRMR = 0.042. The total scale also demonstrated satisfactory reliability, with a Cronbach’s α of 0.879 and a McDonald’s ω of 0.864. Test–retest reliability, assessed using the intraclass correlation coefficient (ICC), showed values ranging from 0.72 to 0.83 across the four factors, whereas the total scale achieved an ICC of 0.86 (95% CI = 0.82–0.91), indicating good temporal stability. AVE and CR values confirmed satisfactory convergent validity and construct reliability. Measurement invariance across gender was supported at configural, metric, and scalar levels. EGA identified four stable and theoretically coherent communities consistent with the factor structure. RFM demonstrated that CMCDAS had the greatest contribution to predicting the overall NPCCDS score. The NPCCDS demonstrated satisfactory validity, reliability, and structural stability for assessing ICU nurses’ perceived competence in comprehensive delirium care. The scale provides a multidimensional and psychometrically robust instrument that can be used for clinical assessment, educational planning, competency monitoring, and evaluation of delirium-related interventions in critical care settings.