Measurement Invariance of Female Sexual Function Index: A study with heterosexual and lesbian Portuguese women

Abstract

The Female Sexual Function Index is a powerful screening tool for female sexual dysfunction extensively used across worldwide. Nonetheless, its factorial structure and psychometric properties have been tested almost exclusively with heterosexual samples. Current study aimed to testing the original factorial structure, reliability and temporal stability in two samples of women (heterosexual and lesbian), and to assess the measurement invariance across sexual orientation. An online sample of 752 Portuguese women (376 lesbian women and 376 heterosexual women) recruited between May 2012 and 2013 participated in the study and completed a sociodemographic questionnaire and the FSFI. For temporal stability, 30 Portuguese women were recruited online in May 2017. Confirmatory factor analysis, reliability analysis and temporal stability were assessed independently for each sample. Measurement invariance (configural, metric, and scalar) was also assessed. Main findings for both samples corroborate the six-factor structure and revealed excellent levels of temporal stability, with Cronbach alphas and McDonalds Omega of .95 for heterosexual sample, and .96 for lesbian women sample. Results corroborate measurement invariance (configural, metric, and scalar) across sample type. Overall, the FSFI revealed a good-fit for the six-factor model in both heterosexual and women sample, with excellent levels of reliability and temporal stability, and showed measurement invariance across sexual orientation. These findings support the use of the FSFI with lesbian women.