Development and psychometric evaluation of the Self-efficacy for Appropriate Medication Use Scale (SEAMS) in low-literacy patients with chronic disease.

Medication nonadherence remains a significant obstacle to achieving improved health outcomes in patients with chronic disease. Self-efficacy, the confidence in one's ability to perform a given task such as taking one's medications, is an important determinant of medication adherence, indicating the need for reliable and valid tools for measuring this construct. This study sought to develop a self-efficacy scale for medication adherence in chronic disease management that can be used in patients with a broad range of literacy skills. The Self-efficacy for Appropriate Medication Use (SEAMS) was developed by a multidisciplinary team with expertise in medication adherence and health literacy. Its psychometric properties were evaluated among 436 patients with coronary heart disease and other comorbid conditions. Reliability was evaluated by measuring internal consistency and test-retest reliability. Principal component factor analysis was performed to evaluate the validity of the SEAMS. Reliability and validity analyses were also performed separately among patients with low and higher literacy levels. The final 13-item scale had good internal consistency reliability (Cronbach's alpha = 0.89). A two-factor solution was found, explaining 52.3% of the scale's variance. The scale performed similarly across literacy levels. The SEAMS is a reliable and valid instrument that may provide a valuable assessment of medication self-efficacy in chronic disease management, and appears appropriate for use in patients with low literacy skills.