How is efficacy for ED treatments measured? What are the IIEF, SEP, and GAQ?

The efficacy of tadalafil has been established in  clinical studies by demonstrating a significant  improvement in erectile function at the end of  the study (‘‘endpoint’’) compared to the start of  the study (‘‘baseline’’) compared to treatment  with placebo. Tadalafil trials typically have  used a co-primary endpoint of change in International  Index of Erectile Function (IIEF) Erectile  Function Domain score, measured at the  end of the trial, and percent of ‘‘yes’’ responses  to Sexual Encounter Profile (SEP) diary questions  2 and 3, recorded after each sexual  encounter during the study:  IIEF: The International Index of Erectile  Function (IIEF) [28] is a 15 question measurement  of erectile function that has been crossculturally  validated.

The IIEF is typically administered  prior to treatment to determine baseline  erectile function and severity, and at  endpoint, to determine the effect of treatment.  The IIEF is a recall instrument that asks the  man to think back over a period of time (typically  4 weeks), then answer each of the 15  questions. Because each question is assessed  on a 0–5 or 1–5 scale, the IIEF score is expressed  as a score. The 15 questions are divided into  five domains (Erectile Function, Orgasmic  Function, Sexual Desire, Intercourse Satisfaction,  and Overall Satisfaction). Six questions  comprise the Erectile Function (EF) Domain  with a score for this domain ranging from 1  to 30. The EF domain is used to determine the  severity of ED [29]. A score  26 is categorized  as ‘‘no erectile dysfunction.’’  SEP: The Sexual Encounter Profile (SEP) diary  is composed of 5 questions. SEP Question 2  (‘‘penetration’’) is ‘‘Were you able to insert  your penis into your partner’s vagina?’’ and  SEP Question 3 (‘‘maintenance’’) is ‘‘Did your  erection last long enough for you to have  successful intercourse?’’ SEP3 is typically  synonymous with ‘‘successful completion’’ or  ‘‘successful intercourse.’’ Men complete the 5  questions in the SEP diary after each intercourse  attempt. Because each question has a  ‘‘yes’’ or ‘‘no’’ response, the SEP ‘‘score’’ is  expressed as a percentage of ‘‘yes’’ responses.  Numerous other efficacy endpoints are also  used and are designated for study purposes as  secondary study endpoints. One common  example is the GAQ, or Global Assessment  Question. The GAQ is a question asked typically  only at the end of the trial. The GAQ asks,  ‘‘Has the treatment you have been taking during  this study improved your erections?’’  Because the GAQ is only asked once at the  end of the study, the GAQ is expressed as the  overall percentage of ‘‘yes’’ responses. Considering  that a yes response to the GAQ does not  necessarily indicate an erection adequate for  intercourse, the authors believe that the SEP3  responses are the most clinically relevant indicators  of successful treatment of ED.