Assessing medication adherence self-efficacy among low-literacy patients: development of a pictographic visual analogue scale

Health behavior interventions are often grounded in Social Cognitive Theory, but instruments used to assess self-efficacy rely on verbal skills and yield scores that are highly positively skewed. Based on a review of the research literature and qualitative research with key informants, a pictographic medication adherence self-efficacy scale was developed. Two studies were conducted to test the pictographic and color visual analogue scale for assessing self-efficacy for medication adherence. Study 1 (N = 81) demonstrated that the pictographic self-efficacy scale was internally consistent (alpha = 0.68), time stable (2-week test-re-test r = 0.63), and showed evidence for convergent and divergent construct validity. Study 2 (N = 64) further supported the reliability of the pictographic self-efficacy scale with additional data supporting its convergent, divergent and criterion-related validity, including associations with medication adherence and HIV viral load. Distributions of self-efficacy scores approximated normal. This newly developed pictographic scale may be useful in assessing medication adherence self-efficacy in lower-literacy populations.