Confirmatory factor analysis of the german version of the international index of erectile function (IIEF):: A comparison of four models

Introduction. The International Index of Erectile Function (IIEF) is the most widely used instrument to assess erectile function in research and clinical practice. However, there are heterogeneous results concerning the factor structure of this questionnaire. The original model assumes five factors (erectile function, intercourse satisfaction, orgasmic function, sexual desire, and overall satisfaction). Others suggested four factors (composite domain of erectile dysfunction and intercourse satisfaction, orgasmic function, sexual desire, and overall satisfaction) or only two factors (sexual function and sexual desire). Because of the high intercorrelation between the different domains, a one-factor model is also plausible. Aims. This study assesses and compares these four models of the German version of the IIEF. Methods. It was examined which of the models fit best our data from 261 German men in cardiovascular rehabilitation participating in the SPARK study (Sexuality of Patients in the Rehabilitation of Cardiovascular Diseases). Contrary to the former exploratory studies, we used confirmatory factor analysis. Main Outcome Measures. Local and global goodness-of-fit measures were calculated. Results. The results show that two items (ability to maintain erection and intercourse frequency) could not be represented sufficiently through any of the four models. Based on the global goodness-of-fit indexes, our data proved to be fairly congruent with the original five-factor model and were acceptably represented by a four-factor model as well. Conclusions. The original five-factor structure could be confirmed. Due to high intercorrelations, the different domains cannot optimally be discriminated and should be interpreted with caution. Further research is needed to clarify the association between the domains of male sexual function.