TheInternational Index of Erectile Function (IIEF-15): psychometric properties of the Portuguese version

Abstract

Introduction: The International Index of Erectile Function (IIEF) is a brief, reliable, and multidimensional scale for assessing sexual function in men in both research and clinical trials.

Aim: The objective of the present study was to determine the psychometric properties of the Portuguese version of the IIEF.

Methods: A total of 1,363 Portuguese men participated in this study (a clinical sample of 37 men and a community sample of 1,326 men).

Main outcome measures: All participants completed a questionnaire regarding demographic information and the IIEF.

Results: Principal component analysis using varimax rotation indicated a two-factor structure explaining approximately 55% of the total variance (one factor encompassing erection and orgasmic function domains of the original IIEF, and a second factor corresponding to sexual desire, intercourse, and overall satisfaction). The differentiated factor structure with five separate domains of sexual function was not replicated in the Portuguese version. The two-factor model and the original five-factor model of male sexual function were assessed with confirmatory factor analysis (CFA), and overall acceptable fits were demonstrated for both models. However, despite a non-optimal performance, CFA provided a better support for the five-factor solution as the model that best fitted the data. An important lack of discriminant validity evidenced by high intercorrelations among dimensions was detected in both models, suggesting a substantial overlap among factors. Reliability studies showed good internal consistency for the five subscales, and test-retest reliability analysis supported the stability of the measure over time. Discriminant validity confirmed the ability of both subscales to differentiate men with erectile dysfunction from matched controls.

Conclusions: Results suggested that the Portuguese version of the IIEF has adequate psychometric properties, and its use is recommended for clinical and research purposes. Further studies are needed in order to elucidate the association among dimensions of male sexual function and, ultimately, to offer a clearer conceptualization of male's sexual response.