Updating the International Index of Erectile Function: Evaluation of a Large Clinical Data Set

The International Index of Erectile Function (IIEF) is the predominant patient-reported outcomes instrument for assessing male sexual function. There are obvious problems with the use of the IIEF in the assessment of an individual patient, such as for men who use injections and men who do not engage in intercourse.

The aim of the current study is to redesign the erectile function domain of the IIEF (IIEF6) to more accurately assess the individual patient.

In an observational study of men undergoing treatment for prostate cancer at a tertiary care institution, including 24,732 questionnaires completed by 6,780 individuals, IIEF6 scores were compared for patients using and not using erectile aids. Men not engaging in sexual intercourse were asked to describe the reason.

The main outcome we were seeking was the IIEF6 scores.

Mean scores before erectile aids items were added was 17.7 compared with predicted scores of 18.3 vs 16.7 if patients reported their function with vs without the use of aids. No intercourse was reported for 35% of surveys. Reasons given were lack of ability or confidence in 53%, lack of willing and available partner in 28%, "other" in 17% (including respondent's or partner's health issues, low libido, preference for nonpenetrative sex or for sex with men). Doubling the sum of the 3 nonintercourse IIEF6 questions had excellent properties (difference of 0.06, limits of agreement -3.10 to 3.22).

Erectile function instruments must include items about erectile aids. Men who report that they have not attempted intercourse should not be assumed to have erectile dysfunction, but should be asked the reason why. For men who report lack of opportunity or preference for intercourse, the score of the 3 nonintercourse IIEF6 questions should be doubled.

This is a large study of patients in a real-world setting. Although the study only includes radical prostatectomy patients, and although the study cohort is not fully representative of the US prostate cancer population as a whole, these issues would not affect the key findings.

The IIEF6 can be redesigned to better assess the individual patient. Vickers AJ, Tin AL, Singh K, et al. Updating the International Index of Erectile Function: Evaluation of a Large Clinical Data Set. J Sex Med 2020;17:126-132.