The Korean Version of the International Index of Erectile Function(IIEF): Reliability and Validation Study

Chung, Tae Gyu; Lee, Tae Kyung; Chung, Sanguk; Lee, Moo Song; Kim, Young Sik; Ahn, Tai Young

Abstract

PURPOSE: The international index of erectile function(IIEF) is a multidimensional scale for assessment of erectile function and detecting treatment-related changes in patients with erectile dysfunction. It was developed by Dr. Rosen in 1997 and composed of 15-item questionnaire of five relevant domains of sexual function(that is, erectile function, orgasmic function, sexual desire, intercourse satisfaction, and overall satisfaction). The IIEF currently is available in more than 30 languages for use in multinational clinical trials, and demonstrates adequate sensitivity and specificity for detecting treatment-related changes in erectile function in patients with erectile dysfunction. For application of the IIEF to Korean, it is inevitable to demonstrate the reliability and validity of Korean version of IIEF, since the cultural background is one of the most important factors which often results in misinterpretation of the questionnaire.
MATERIALS AND METHODS
From May 13th to July 20th 1998, a total of 39 patients aged over 30 who visited Andrology Clinic with the complaint of erectile dysfunction were enrolled for the patient group and 40 age-matched volunteers who visited the Department of Family Medicine without erectile dysfunction were enrolled for a control group. Self administered questionnaire survey was performed with linguistically valid Korean version of IIEF for all study subjects and was repeated with the inteval of 10-25 days(between the first and second survey). The results were analyzed statistically by PC-SAS version 6.12.
RESULTS
Two separate aspects of scale reliability were evaluated, namely, internal consistency and test-retest repeatability. Internal consistency(Cronbach`s alpha) was computed separately for the five domains in patient and control group. Responses in overall satisfaction was highly consistent with alpha value of 0.96. A satisfactory degree of consistency also was observed for items in the other domains(alpha values greater than 0.70). Test-retest repeatability was assessed by computing correlations between the domain score and total scale scores at the first and the second survey. There was no significant difference in the domain scores and total scale scores between the first and the second survey; nevertheless, test-retest repeatability was relatively low for the orgasmic function(r=0.67) and intercourse satisfaction(r=0.70) domains. Relatively high correlations were observed for the other domains(r value of 0.73 to 0.85), as well as for the total scale scores(r=0.88)(p<0.01). To demonstrate validity, domain scores were compared with the monthly frequency of sexual intercourse(convergent validity) and with scales that measure occupational satisfaction(divergent validity). Siginificant positive correlations were observed between the monthly frequency of sexual intercourse and subscale scores for all five domains. In contrast, none of the correlations between domain scores and measure of occupational satisfaction reached statistical significance. Discriminant validity was assessed by comparing the responses for patients with erectile dysfunction with control group by repeated measures ANOVA. Highly significant differences were observed between the patients with erectile dysfunction and age-matched controls.
CONCLUSIONS
Based on the results of this study, the Korean version of IIEF was verified in its reliability and validity. This can be used as a brief and reliable self-administered scale for assessing erectile function and for detecting treatment-related changes in patients with erectile dysfunction. Furthermore, this can be used as universal and objective scale in multinational clinical trial and research field.