Simplified Interpretation of the Erectile Function Domain of the International Index of Erectile Function

This report describes a post hoc analysis of data from a randomized, double-blinded, placebo-controlled, flexible-dose, sildenafil trial in men with erectile dysfunction.

To simplify interpretation of erectile function (EF) domain scores of the International Index of Erectile Function (IIEF).

Men at least 18 years old with erectile dysfunction were randomized to receive sildenafil or placebo for 12 weeks. Men taking nitrates or nitric oxide donors were excluded. Responses for each IIEF EF domain question (questions 1-5 and 15) were combined into two broad categories ("success" for responses of the two most favorable categories of a question and "no success" for other responses). Each question was expressed in a logistic regression model (sildenafil and placebo groups combined) as a function of overall EF domain score.

IIEF EF domain score and items.

A four-point increase in the IIEF EF domain score was associated with an odds ratio of success of 6.1 for getting an erection, 29.2 for having a firm erection, 10.0 for able to penetrate,12.8 for maintaining erection, 4.0 for maintaining erection to completion, and 3.7 for erection confidence. An EF domain score of 22 was associated with a probability of success of 81% for getting an erection, 86% for having a firm erection, 89% for able to penetrate, 67% for maintaining an erection, 70% for maintaining an erection to completion, and 32% for erection confidence. For an EF domain score of 16, the corresponding probabilities of success were 22%, 4%, 20%, 4%, 22%, and 6%, respectively.

These results provide stakeholders with a simplified and meaningful interpretation of IIEF EF domain scores based on six key aspects of EF.