Measurement Equivalence of the Self-Care of Chronic Illness Inventory Across Time: Longitudinal Structural Equation Models

BACKGROUND AND OBJECTIVES: The Self-Care of Chronic Illness Inventory (SC-CII) is a theoretically grounded instrument comprising three scales measuring self-care maintenance, monitoring and management behaviors in adults with chronic illnesses. Although its validity and reliability have been demonstrated in cross-sectional studies, the stability of its psychometric properties over time has not been examined. This study aimed to test the longitudinal measurement equivalence of the three SC-CII Scales. RESEARCH DESIGN AND METHODS: Longitudinal measurement equivalence was assessed over a 12-month period using a Confirmatory Factor Analysis (CFA) approach. Patients aged 65 or older with multiple chronic conditions (MCCs) were enrolled. Four increasingly restrictive level of invariance were tested: configural, metric, scalar and strict invariance at the first and second-order level. RESULTS: Participants (N = 630) had a mean age of 77 years, were mostly female. For the Self-Care Maintenance scale, full metric invariance and partial scalar and strict invariance were achieved at both first- and second-order levels. For the Self-Care Monitoring scale, full metric and scalar invariance, and partial strict invariance were established. For the Self-Care Management scale, full metric, full scalar (first-order), partial scalar (second-order) and partial strict (first- and second-order) were achieved. DISCUSSION AND IMPLICATIONS: The SC-CII proved to be longitudinally stable, confirming its suitability for repeated assessments of self-care. The SC-CII can be confidently used by nurses to monitor self-care behaviors and evaluate changes during the disease trajectory, supporting the development of personalized interventions tailored. This study demonstrated the SCCII's temporal equivalence, strengthening its use in clinical and research settings.