A comparison of the International Index of Erectile Function and erectile dysfunction studies

Authors


S. Carrier, Division of Urology, McGill University, 687 Pine avenue West, Montreal, Quebec, Canada H3A 1A1.
e-mail: serge.carrier@mcgill.ca

Abstract

OBJECTIVE

To evaluate the ability of the five-item version of the International Index of Erectile Function (IIEF-5) to diagnose the vascular aetiology and severity of erectile dysfunction (ED), and to compare it with pharmacological testing and duplex Doppler ultrasonography, as such questionnaires are widely used by the pharmaceutical industry to categorize the severity of ED and to assess the efficacy of drug therapy.

PATIENTS AND METHODS

In all, 80 patients (mean age 45.2 years, sd 14.0; mean duration of ED 3.5 years) were reviewed by an examiner unaware of their IIEF scores during testing. Penile blood flow was assessed in each patient after an intracavernosal injection with prostaglandin-E1 (10 µg), with self-stimulation in privacy. The peak systolic velocity, end diastolic velocity and resistive index were measured for the vascular diagnosis. Visual ratings of erectile responses were also used for analysis.

RESULTS

Of the 80 patients, 30 had a normal vascular response, 38 arterial insufficiency and 12 were diagnosed with venous leakage. There was no significant difference in the IIEF scores among patients with a normal vascular response, arterial insufficiency or venous leakage. Analysis of visual ratings of erections showed no difference in IIEF scores among the different groups of patients.

CONCLUSION

The IIEF was designed and developed specifically for assessing and evaluating sexual function in clinical trials. However, as shown here, the IIEF cannot and should not be used as a tool to diagnose or compare specific vascular causes of ED.

INTRODUCTION

Erectile dysfunction (ED) is defined as the inability to achieve or maintain an erection sufficient for satisfactory sexual activity [1]. Evidence-based approaches in the diagnosis of ED have included cavernosometry, nocturnal penile tumescence testing, and penile blood-flow studies (PBFS). In the clinical office an excellent and fast response to intracavernosal vasoactive agents (in neurologically normal men) may support the diagnosis of psychogenic impotence [2]. PBFS provide an objective, minimally invasive evaluation of a suboptimal/equivocal erectile response [3]. Although laboratory-based diagnostic procedures are available, recently sexual questionnaires have gradually replaced them for evaluating ED because they are easy to use.

The International Index of Erectile Function (IIEF, a 15-item self-administered questionnaire scale) is a brief and reliable measure of ED that is culturally, linguistically and psychometrically valid [4]. The IIEF has been widely used for determining the efficacy of treatments in controlled clinical trials. It is suitable for use by clinicians and researchers, and minimally burdensome to patients. The five domains of the IIEF are erectile function (six items), orgasmic function (two items), sexual desire (two items), intercourse satisfaction (three items), and overall satisfaction (two items). An abridged five-item version of the 15-item IIEF, the IIEF-5, was developed to diagnose the presence and severity of ED [5,6]; it has already been used for evaluating pharmacological therapy for ED, and in clinical trials.

It is unclear whether the IIEF-5 is capable of diagnosing the severity and cause of ED. The present study aimed to evaluate the ability of the IIEF-5 to differentiate among the vascular aetiology and severity of ED, and to compare it with pharmacological testing and duplex Doppler ultrasonography (DUS).

PATIENTS AND METHODS

From May 2000 to November 2001, 80 patients (mean age 45.7 years, sd 14.2; mean duration of ED 3.5 years) were studied prospectively; all patients completed the IIEF before meeting the physician, who was unaware of the scores from the IIEF questionnaire. The indications for DUS were: young age, trauma, requests from patients, or medico-legal reasons. All DUS was undertaken by the same examiner (S.C.). Only the five specific questions about erectile function were used for the analysis (Appendix); a score of 1–5 was given for each question. All patients underwent a complete history and physical examination. The scores of the IIEF-5 were divided into normal (> 21), mild (16–21), moderate (11–15), or severe (< 11). Patients underwent penile DUS (8.0 MHz biplanar transducer, B&K Medical, Boston, MA) 5 min after an intracavernosal injection with 10 µg of prostaglandin-E1[7]; the patients were then allowed privacy for self-stimulation (and relaxation) and the DUS repeated thereafter. Flows associated with the best erectile responses were used for analysis. The physician confirmed that during DUS the patient obtained either a similar or better erection at the office than at home. The cavernosal artery peak systolic velocity (PSV), end-diastolic velocity (EDV), and resistive index (RI) were measured. Patients with a PSV of> 30 cm/s and RI of> 0.90 were classified as having a normal vascular response, with a PSV of> 30 cm/s and RI of < 0.80 as having vascular leakage (VL), and with a PSV of < 30 cm/s and RI of < 0.90 as arterial insufficiency (AI) [8–12]. The visual rating scale of the erections obtained after injection with prostaglandin was noted as ‘none’, ‘erections inadequate for penetration’, ‘adequate for penetration’, or ‘fully rigid’. The results were analysed statistically using Student's t-test and the Kruskal–Wallis anova.

RESULTS

Of the 80 patients, 33 were smokers or ex-smokers, eight had hypertension, 10 hypercholesterolaemia, five diabetes, and five coronary artery disease. PBFS (Table 1) showed that 30 patients had a normal vascular response, 38 AI and 12 VL; the mean IIEF for the three groups is also shown in Table 1. There was no significant difference in the IIEF scores among the three groups (P > 0.05) and the analysis of the visual ratings of erections after injection with prostaglandin also showed no differences in IIEF scores among the different visual scales; P > 0.05 (Table 2).

Table 1.  The results of penile DUS and a summary of the different severity of IIEF scores
VariableNormalAIVL
DUS, mean (sem)
PSV, cm/s44.4 (12.4)23.9 (6.9)44.8 (11.3)
EDV, cm/s  2.5 (1.1)  4.0 (2.4)  8.5 (3.8)
RI  0.94 (0.04)  0.80 (0.11)  0.70 (0.06)
IIEF10.3 (5.1)  8.3 (5.1)12.1 (4.3)
IIEF severity, no. of patients
slight  5  5  3
moderate11  8  4
severe1425  5
Table 2.  The distribution of IIEF-5 scores among various visual ratings of erections with prostaglandin-E1
Erectile
response
No. of
patients
PSV, cm/sRIIIEF
Inadequate1823.50.73  5.5
Adequate4232.60.8710.7
Full2039.20.90  9.4

DISCUSSION

Over the past few years, to better and more easily assess the outcome of clinical trials, sexual questionnaires have been developed to measure changes over time with treatment. These questionnaires have become widely used in categorizing the severity of ED and for assessing the efficacy of drug therapy. These tools are quick and less invasive than the previous historical approaches that typically included either cavernosometry, nocturnal penile tumescence testing, and/or PBFS.

Rosen et al.[4] showed the IIEF to be a sensitive and specific tool for investigating male sexual dysfunction. The IIEF is the most widely used self-administered questionnaire, and has been validated in several languages. In 1999, an abridged five-item version of the IIEF-15 was developed to diagnose the presence and severity of ED. The five items were selected based on their ability to identify the presence or absence of ED in accordance with the National Institute of Health's definition of ED. These items focused on erectile function and intercourse satisfaction [5].

As these types of questionnaires have been incorporated in trials of the efficacy of drug therapy, we wished to assess whether they are able to differentiate among the various causes of ED. Initially, the IIEF was designed to assess changes over time in ED and not to diagnose ED per se. Currently physicians are using not only the IIEF but also other questionnaires to diagnose ED. Urologists will soon encounter a variety of cause-specific pharmacotherapies where the IIEF may be insufficient for evaluating and managing patients with ED. In the present study, there was no significant difference between the IIEF-5 scores of patients with ED and a normal DUS vascular response and those with a vascular response consistent with AI or VL. In addition, patients with a normal vascular response had severely abnormal IIEF scores. For the visual response to pharmacotherapy there was no significant difference between the IIEF-5 scores among patients with different causes of ED; severely abnormal IIEF-5 scores were also recorded in all categories of the visual rating of erections.

We agree that DUS might not be the ultimate test for evaluating organic ED; the prime factor in establishing an accurate evaluation of ED using DUS is that the patient is fully relaxed, although exactly when this state is achieved is controversial. During the test, if the patient can obtain an erection similar to those ‘at home’, at least the patient (or the penis) is as relaxed as ‘normal’; thus we consider that the vascular evaluation is close to reality.

The penile DUS test should be used whenever it might affect the patient's management. As the indications to use DUS in the present study were limited to younger men, after trauma, by request from the patients, or for medico-legal reasons, it may explain why the mean age was lower than usually reported. Thus obviously the population selected might affect the results of this study and may not be representative of the general population with ED.

Although the IIEF neither statistically differentiated among the specific vascular causes of ED (and was never intended for this purpose) nor provided an accurate prediction of pharmacological testing, it is still a useful tool in the initial evaluation of ED. In clinical trials it is an excellent tool, especially to assess changes over time in a patient, because it has a high degree of internal consistency. However, it must be used prudently when comparing different causes of ED.

APPENDIX

Specific erectile questions of the IIEF-5; all answers are graded 1–5.

Over the past 3 months:

  • 1How do you rate your confidence that you can get and keep an erection?Answers: ‘very low’, ‘low’, ‘moderate’, ‘high’, ‘very high’.
  • 2When you had erections with sexual stimulation, how often were your erections hard enough for penetration?Answers: ‘almost never/never’, ‘a few times’ (much less than half the time), ‘sometimes’ (about half the time), ‘most of the time’ (much more than half the time), ‘almost always/always’.
  • 3During sexual intercourse, how often were you able to maintain your erections after you had penetrated your partner?Answers: as Question 2.
  • 4During sexual intercourse, how difficult was it to maintain your erection to the completion of intercourse?Answers: ‘extremely difficult’, ‘very difficult’, ‘difficult’, ‘slightly difficult’, ‘not difficult’.
  • 5When you attempted sexual intercourse, how often was it satisfactory for you?Answers: as Question 2.
Abbreviations
ED

erectile dysfunction

AI

arterial insufficiency

VL

venous leakage

PSV

peak systolic velocity

EDV

end-diastolic velocity

RI

resistive index

IIEF

International Index of Erectile Function

PBFS

penile blood-flow studies

DUS

Doppler ultrasonography.

Ancillary