The short medication adherence scale (SMAS-7): Development and psychometric validation in a general population sample

Background: Medication adherence is essential for treatment success across both chronic and acute conditions. However, concise, multidimensional, and broadly applicable validated tools to measure medication adherence remain scarce. Objectives: This study primarily aimed to develop and validate the Short Medication Adherence Scale (SMAS-7) and, secondarily, to assess adherence levels and related factors in a general adult population. Methods: A cross-sectional study was conducted among Lebanese adults aged ≥18 years from the general population. Individuals who declined follow-up contact for the test-retest phase were excluded. The 7-item SMAS-7, developed from the LMAS-14, was administered electronically in Arabic using an online questionnaire. Exploratory and confirmatory factor analyses (EFA and CFA) were performed on two random subsamples to assess factorial structure and model fit. Internal consistency (Cronbach's α, McDonald's ω), test-retest reliability (ICC), and construct and criterion validity were evaluated. Multivariable logistic regression identified predictors of adherence using a ROC curve-derived SMAS-7 cut-off score. Results: A total of 501 participants were included in the study. EFA revealed a 3-factor structure, psychological, economic, and behavioral domains, supported by KMO = 0.830 and significant Bartlett's test (P < 0.001). CFA confirmed the structure with excellent fit (χ²/df = 1.757, CFI = 0.992, TLI = 0.985, RMSEA = 0.055, SRMR = 0.020). The SMAS-7 demonstrated high internal consistency (α = 0.889, ω = 0.945) and test-retest reliability (ICC = 0.779). Criterion validity was excellent (AUC = 0.985; sensitivity = 91.2 %; specificity = 96.0 %). Suboptimal adherence was observed in 52.3 % of participants. Significant predictors of adherence included gender (P = 0.030), region (P = 0.014), financial well-being (P = 0.002), chronic illness (P = 0.009), communication barriers (P = 0.013), and patient perception (P = 0.029). Conclusion: The SMAS-7 demonstrated strong preliminary psychometric properties in this initial validation study. It offers a valuable resource for researchers, clinicians, and policymakers seeking to monitor and enhance adherence behaviors. While these findings are encouraging, further studies in diverse populations and clinical settings are required to confirm its external validity and generalizability. The findings revealed suboptimal adherence and underscored the multifaceted nature of its predictors, highlighting the need for targeted, multidimensional interventions.