Measuring self-efficacy to use vaginal microbicides: the Microbicide Use Self-Efficacy instrument

Objectives To evaluate the psychometric properties of the Microbicide Use Self-Efficacy (MUSE) instrument and to examine correlates of self-efficacy to use vaginal microbicides among a sample of racially and ethnically diverse women living in the north-eastern United States.

Exploratory and confirmatory factor analytic methods were used to explore and determine the dimensionality and psychometric properties of the MUSE instrument. Construct validity was assessed by examining the relationships of the MUSE instrument to key sexual behaviour, partner communication, relationship and psychosocial variables.

Two dimensions of self-efficacy to use microbicides were psychometrically validated and identified as 'Adherence and Access' and 'Situational Challenges.' The two four-item subscales measuring Adherence and Access and Situational Challenges had reliability coefficients of 0.78 and 0.85, respectively. Correlates of the two measures were tested at a Bonferroni-adjusted α level of P=0.001, and 19 of 43 variables analysed were found to significantly relate to Adherence and Access, whereas 16 of 43 variables were significantly related to Situational Challenges. Of the 35 significant relationships, 32 were in the domains of partner communication, partner relationships, and behavioural and psychosocial variables.

The MUSE instrument demonstrated strong internal validity, reliability and initial construct validity. The MUSE instrument can be a useful tool in capturing the multidimensional nature of self-efficacy to use microbicides among diverse populations of women.