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 a = 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.
Keywords : self-efficacy; medication adherence; literacy; chronic disease; reliability; validity
Despite the availability of many effective drug therapies for the management of chronic diseases, patient nonadherence to prescribed medications remains a major obstacle to the therapeutic success of such drugs (Bodenheimer, Lorig, Holman, & Grumbach, 2002; Haynes et al., 2005). A recent survey of American adults revealed that in the past 12 months, 18% of respondents had failed to fill a prescription, 26% had delayed filling a prescription, 14% had taken a prescription medication in smaller doses than prescribed, and 30% had taken a prescription medication less often than prescribed (The Boston Consulting Group, 2003). Prior research has demonstrated that over a 1-year period, only 50-60% of patients are adherent with taking prescribed medications (DiMatteo, 2004; Osterberg & Blaschke, 2005). Recognizing the negative impact on patients' health of medication nonadherence is important for nurses and physicians alike to strive toward improving this crucial health behavior. This need led to the development of the Self-efficacy for Appropriate Medication Adherence Scale (SEAMS) to give nurses and physicians a tool to better understand and approach medication adherence in patients with low literacy skills.
BACKGROUND AND CONCEPTUAL FRAMEWORK
Several behavioral theories have been applied to the study of medication adherence (Leventhal & Cameron, 1987). Bandura's Social Cognitive Theory appears to offer a particularly useful framework (Bandura, 1986). Self-efficacy, the key construct in that theory, refers to the belief or confidence that one can successfully perform a specific action required to attain a desired outcome. Bandura proposed that self-efficacy is the most important prerequisite for behavior change, and it is accepted as an important aspect of disease management (Bodenheimer et al., 2002). Self-efficacy is also an important predictor of medication adherence (Burke, Dunbar-Jacob, & Hill, 1997; Molassiotis et al., 2002; Ni et al., 1999; Scherer & Bruce, 2001).
While a number of instruments to measure medication self-efficacy have been developed, many are designed for specific diseases or populations (Ogedegbe, Mancuso, Allegrante, & Charlson, 2003; Resnick, Wehren, & Orwig, 2003), and few are broadly applicable across a range of chronic diseases (Denhaerynck et al. …