Abstract
INTRODUCTION: Family-reported outcome measures are essential to assess the impact of illness and care on family caregivers in palliative care (PC). The Medical Outcomes Study Social Support Survey - MOS-SSS is widely used to measure perceived social support. However, the number of validated versions for Spanish-speaking caregivers in PC contexts remains limited. This study aimed to evaluate the psychometric properties of the MOS-SSS in a Colombian sample of family caregivers of patients with advanced illness receiving palliative care. METHODS: A psychometric cross-sectional study was conducted with caregivers of patients with cancer and heart failure receiving PC in two hospitals in Medellín-Colombia. The instrument was administered through structured interviews conducted by trained researchers. Construct validity was assessed using confirmatory and exploratory factor analyses. Internal consistency, stability, convergent and known-groups validity, and sensitivity to change were evaluated. The analyses followed COSMIN guidelines. RESULTS: A total of 434 family caregivers (mean age = 45.7 ± 14.6 years; 86% female) of patients receiving PC were included. Confirmatory factor analysis supported a four-factor model with acceptable fit indices (CFI = 0.94, TLI = 0.92, RMSEA = 0.07, SRMR = 0.043), although a high covariance was observed between the domains of positive social interaction and affectionate support (r = 0.899). An EFA revealed a three-factor model with acceptable fit and theoretical coherence (CFI = 0.94, TLI = 0.920, RMSEA = 0.073, and SRMR = 0.044). Cronbach's alpha for the total scale was 0.94, and McDonald's Omega was 0.96. Stability was good to excellent (0.85-0.89). Convergent validity was confirmed using the Quality of Life in Life Threatening Illness-Family Carer Version scale (rho = 0.426, p < 0.001), and known-groups validity showed lower scores among sole caregivers. The scale was not sensitive to changes following a brief educational intervention. DISCUSSION: The Spanish version of the MOS-SSS demonstrated strong psychometric properties for assessing perceived social support in family caregivers within PC. The findings support its use in clinical and research settings in Latin American contexts. Future research should explore the responsiveness of interventions explicitly designed to modify the social support networks of caregivers.