The 6-item InCharge financial distress/financial wellbeing (IFDFW-6) scale: Development and validation in pharmacy and epidemiology research

Background: Financial wellbeing and distress have emerged as key social determinants influencing health behaviors, medication adherence, and quality of life. Yet, these constructs remain underexplored in pharmacy and epidemiology research due to the lack of brief, validated, and context-appropriate measurement tools. The widely used InCharge Financial Distress/Financial Wellbeing (IFDFW-8) scale offers strong psychometric evidence but includes items that may not reflect health-related financial strain and may increase respondent burden. Objective: This study aimed to develop and validate a concise, contextually applicable 6-item version (IFDFW-6) for use in pharmacy and epidemiological research. Methods: A cross-sectional study was conducted among adults who had recently visited community pharmacies. The questionnaire included validated measures of financial wellbeing (IFDFW-8), medication adherence (SMAS-7), patient experience and satisfaction (MA-PSQ-18), and quality of life (EQ-5D-5L). Exploratory and confirmatory factor analyses (EFA, CFA) evaluated dimensionality; reliability was examined using Cronbach's α and McDonald's ω; criterion validity was tested against the IFDFW-8 using ROC analysis; and measurement invariance was assessed across gender, health status, and healthcare access groups. Results: Among 501 participants, EFA supported a unidimensional structure explaining 84.3% of variance (factor loadings = 0.878–0.946). CFA confirmed excellent model fit (CFI = 0.997, RMSEA = 0.056, SRMR = 0.008). The IFDFW-6 demonstrated high internal consistency (α = 0.963; ω = 0.963) and strong criterion validity against the parent IFDFW-8 (AUC = 0.993; cutoff = 29.5, sensitivity = 95.8%, specificity = 95.2%). Higher financial wellbeing correlated with better quality of life, greater satisfaction with pharmacy services, and higher medication adherence. Conclusion: The IFDFW-6 is a reliable and valid instrument that efficiently captures financial wellbeing/distress and has been refined for contextual applicability in pharmacy and epidemiology research, supporting the integration of economic determinants into health-related studies. • The IFDFW-6 showed a unidimensional structure confirmed by EFA and CFA. • The scale demonstrated excellent internal consistency (α = 0.963; ω = 0.963). • Criterion validity was outstanding (AUC = 0.993). • Measurement invariance was established across gender, health status, and healthcare access. • Higher financial wellbeing correlated with greater medication adherence, patient satisfaction, and QOL.