The HIV Medication Taking Self-efficacy Scale: psychometric evaluation

Aim. This paper is a report of an examination of the psychometric properties of the HIV Medication Taking Self-efficacy Scale. Background. Self-efficacy is a critically important component of strategies to improve HIV medication-taking; however, valid and reliable tools for assessing HIV medication-taking self-efficacy are limited. Method. We used a cross-sectional, correlational design. Between 2003 and 2007, 326 participants were recruited from sites in Pennsylvania and Ohio in the United States of America. Six self-report questionnaires administered at baseline and 12 weeks later during 'Improving Adherence to Antiretroviral Therapy' were used to examine the variables of interest. Means and variances, reliability, criterion, and construct validity of the HIV Medication Taking Self-efficacy Scale were assessed. Findings. Participants reported high self-confidence in their ability to carry out specific medication-related tasks (mean=8.31) and in the medication's ability to effect good outcomes (mean=8.56). The HIV Medication Taking Self-efficacy Scale and subscales showed excellent reliability (alpha=0.93 similar to 0.94). Criterion validity was well-established by examining the relationships between the HIV Medication Taking Self-efficacy Scale and selected physiological and psychological factors, and self-reported medication adherence (r=-0.20 similar to 0.58). A two-factor model with a correlation between self-efficacy belief and outcome expectancy fitted the data well (model chi(2)=3871.95, d.f.=325, P<001; CFA=0.96; RMSEA=0.046). Conclusion. The HIV Medication Taking Self-efficacy Scale is a psychometrically sound measure of medication-taking self-efficacy for use by researchers and clinicians with people with HIV. The findings offer insight into the development of interventions to promote self-efficacy and medication adherence in persons with HIV.