Measurement of Male and Female Sexual Dysfunction Raymond C. Rosen, PhD

Address disorders are less well understood presently, efforts are Department of Psychiatry, UMDNJ-Robert Wood Johnson underway to refine the diagnosis and classification of these Medical School, 675 Hoes Lane, Piscataway, NJ 08854, USA. disorders [5]. An important contributing factor to this E-mail: [email protected] field has been the development of validated instruments for Current Psychiatry Reports 2001, 3:182–187 the assessment of sexual function. These instruments have Current Science Inc. ISSN 1523-3782 Copyright © 2001 by Current Science Inc. been used as primary endpoints in clinical trials, as well as for clinical screening and diagnostic purposes. Not surpris- ingly, most attention thus far has been directed towards Measurement approaches for male and female sexual development of validated instruments for assessment of ED. dysfunction have proliferated in recent years, spurred in Sexual dysfunctions in men and women are classified large part by the development of new treatments for male according to the four-phase model of Masters and Johnson and female dysfunction. In the past, physiologic measures [6] and Kaplan [7]. This is briefly as follows: of penile tumescence and rigidity in males, and vaginal Sexual desire, the first phase, consists of the motiva- blood flow in females, played an important role in clinical tional or appetitive aspects of sexual response. Sexual and research studies. More recently, a variety of brief, urges, fantasies, and wishes are included in this phase. self-report measures have been developed for assessing Sexual excitement refers to a subjective feeling of male and female function across a variety of sexual sexual pleasure and accompanying physiologic changes. domains (eg, desire, arousal, orgasm, satisfaction). These This phase includes penile erection in men and vaginal self-report measures have been shown to have a high lubrication in women. degree of reliability and validity, and are sensitive to Orgasm, or climax, is defined as the peak of sexual treatment interventions. Accordingly, they are widely pleasure, with rhythmic contractions of the genital employed in clinical trials. Daily diary or sexual event musculature in both men and women, as well as ejacu- logs have similarly been developed for this purpose. Self- lation in men. report measures have been used for clinical screening The final phase is resolution, during which a general purposes and for diagnostic assessment of sexual function sense of relaxation and well-being is experienced. In men, in a number of studies. Finally, several disease-specific a refractory period for erection and ejaculation usually quality of life and treatment satisfaction measures have occurs during this phase. The sexual dysfunctions can been developed, which are currently in widespread use be considered as alterations in one or more phases of the in clinical trials of sexual dysfunction. sexual response cycle, and this four-stage model forms the basis for diagnosis and classification of the sexual dysfunc- tions in DSM-IV (Diagnostic and Statistical Manual of Mental Introduction Disorders, Fourth Edition) [8]. Sexual dysfunctions are highly prevalent, affecting about Measurement instruments for sexual dysfunction focus 43% of women and 31% of men overall [1,2]. In addition to on assessing changes or disruption in one or more of these their widespread prevalence, sexual dysfunctions have phases. Physiologic measures are generally directed at been found to impact significantly on interpersonal assessing arousal responses, including penile tumescence functioning and overall quality of life in both men and and rigidity in men [9•10] or vaginal vasocongestion in women. Although less prevalent overall than sexual desire women [11], in response to endogenous events (eg, noctur- difficulties, sexual arousal difficulties in men and women nal penile erection) or exogenous stimulation (eg, visual have received special attention in recent years. A broad range sexual stimulation). These measures are currently used of organic and psychologic risk factors, including more often for research than clinical purposes. In contrast, diabetes, cardiovascular disease, smoking, and depression self-report or questionnaire measures are typically multi- have been associated with arousal disorders in both sexes dimensional instruments that assess sexual functioning [3•]. Effective treatment of erectile dysfunction (ED) has in across a number of domains, including desire, arousal, turn been associated with marked improvements in mood orgasm, and satisfaction. Several new questionnaire state and quality of life [4]. Although female sexual instruments have been developed in recent years, which Measurement of Male and Female Sexual Dysfunction • Rosen 183 have played an important role in clinical trials of male and diagnostic classification [14]. Additional limitations of female sexual dysfunction. Clinical trials have also the device include lack of adequate standardization of included daily diaries or sexual event logs for measurement normal values, limited time sampling of tumescence and of daily sexual activities. Finally, several instruments have rigidity, and potential intrusiveness of the device for some been developed for assessment of life satisfaction or patients. Despite these limitations, Rigiscan assessment quality of life changes associated with sexual dysfunction of penile tumescence and rigidity continues to play an in men and women. important role as an objective and quantifiable measure of erectile response. Other physiologic measures of penile tumescence and Physiologic Measures rigidity include volumetric and strain-gauge plethysmo- As noted above, several objective or physiologic measures graphy [15], and the erectiometer [16]. Volumetric plethys- are available for assessment of sexual arousal responses in mography provides a highly sensitive measure of penile males and females. These have typically focused on the engorgement, which has been used extensively in studies assessment of penile erection and rigidity in men, and of sexual preference or paraphilias [17–19]. However, the vaginal blood flow or vasocongestion in women. Although measurement apparatus is obtrusive and inconvenient studies of nocturnal erection were used extensively in the to use, and provides no information on penile rigidity. 1980s and 1990s for diagnostic assessment of organic Similarly, mercury-in-rubber and electromechanical strain- erectile dysfunction, this technique has declined in use gauges provide sensitive measures of penile circumference since the availability of sildenafil. Currently, physiologic change and have been widely used in laboratory studies of assessment methods are used predominantly for research sexual arousal [20–22]. in clinical trials of male and female sexual dysfunction. Finally, the erectiometer provides a crude measure of Among the methods for physiologic assessment of both rigidity and tumescence (circumference change). This penile rigidity and engorgement [9•,10], the most widely device consists of a 2-cm wide felt band with a sliding used is the Rigiscan system (Timm Medical Systems, Eden collar fastened to one end. The felt band expands with Prairie, MN). This method was first described by Bradley tumescence, but requires a force of about 250 grams to and Timm [9•], who recommended use of the device in initiate expansion. In this way, the device provides a the home setting for monitoring of nocturnal penile combined assessment of both circumference and rigidity tumescence and rigidity (NPTR). The device is attached to changes [16]. It has been used to differentiate response the patient's inner thigh, with two loops placed around the patterns in clinical studies with normal and sexually base and tip of the penis proximal to the coronal sulcus. dysfunctional men [23,24], although the erectiometer Measures of radial rigidity are obtained by application of a provides less sensitivity and reliability than either the predetermined force to each loop every 3 minutes initially, Rigiscan or mercury strain gauge devices [24]. and at 30-second intervals when an increase of more than In women, the most widely used method for assessing 10 mm at the base is detected. Penile rigidity is expressed sexual arousal is the vaginal photoplethysmograph as a function of displacement when the loop is tightened [11,25•]. This device consists of a light-emitting diode and around the penis, and rigidity is defined in terms of penile sensitive photocell detector enclosed in a tampon-sized, stiffness as determined by cross-sectional response to clear acrylic probe. The signal obtained reflects changes in radial compression [9•]. Although the technique was the amount of light back-scattered to the photocell from developed originally for home monitoring of NPTR, the surrounding vasculature, and provides a sensitive, Rigiscan recording has recently been used for in-clinic albeit indirect, measure of vaginal vasoengorgement. assessment of penile tumescence and rigidity in response Depending upon the mode of recording, measures of to pharmacologic or visual sexual stimulation (VSS). vaginal blood volume or vaginal pulse amplitude (VPA) Several potential limitations have been identified, the can be obtained. VPA is regarded as the more sensitive and most significant of which is the assumption of equivalence reliable measure [25•], and is more often used in studies of between radial and axial rigidity. Although there is limited treatment outcome. Although this method has been used evidence for this assumption, at least one study compared in a variety of research settings, it is not well standardized measurements of axial and radial rigidity at constant and there is no clinical application of the procedure to corporal pressures [12]. Axial and radial rigidity were date. Other methods for assessing female genital vasocon- found to be functionally related, and both measures were gestion, such as measures of labial temperature or clitoral moderately correlated with intracavernous pressure. In a blood flow, have also been described, although these are comparison of Rigiscan with sleep laboratory measures of not widely used at present. tumescence and rigidity, Licht et al. [13] reported that a base rigidity of 55% or more predicted functional erection, with a sensitivity of 85% and specificity of 91%. Other Self-report Measures investigators have reported that tip rigidity of 70% Self-report measures of sexual function are divided into for greater than 5 minutes provides the best cutoff for three major categories: self-administered questionnaires, 184 Sexual Dysfunction daily diaries or event logs, and structured interviews. Each treatment responsiveness. The scale has had limited use in of these approaches has been used in recent clinical trials, large-scale clinical trials of ED. although the primary emphasis in most validation studies has been on self-administered questionnaires. These Center for Marital and Sexual Health Questionnaire measures have the potential advantage of providing This brief 18-item self-report questionnaire assesses standardized and relatively cost-efficient assessment of current sexual function in the areas of erection, orgasm, current and past sexual functioning. Patient burden is desire, and satisfaction [32]. Initial psychometric assess- generally low, and some measures have been designed ment of the instrument has been performed, although data specifically for use in multicenter, clinical trials [26•,27•]. regarding sensitivity and specificity are lacking. In this Some of these measures are also in use clinically for screen- study, the measure showed adequate reliability and ing and assessment of sexual function in men or women. construct validity. It has had minimal use to date in clinical The questionnaire measures most widely used in men at trials of ED. present are listed below. Female Sexual Function Index International Index of Erectile Function This is a recently developed, brief (19-item) self-report The International Index of Erectile Function (IIEF) was questionnaire which assesses sexual functioning in women designed and developed specifically for assessment of male in six separate domains (desire, arousal, lubrication, sexual function in clinical trials [26•]. The IIEF has been orgasm, satisfaction, pain) [27•]. In addition, a total scale extensively validated and widely used as a measure of score can be computed according to a simple scoring efficacy in clinical trials of ED agents. The instrument algorithm. The questionnaire was developed for use in consists of 15 items and assesses sexual functioning in five clinical trials of female sexual dysfunction and was domains: erectile function, orgasmic function, sexual validated in a multicenter study of women with sexual desire, intercourse satisfaction, and overall satisfaction. arousal disorder (n = 128) and age-matched controls Average scores are calculated in each of the major domains, (n = 131). The measure was shown to have a high degree and a simple severity algorithm is available for clinical of internal consistency and test-retest reliability, and differ- interpretation of scores on the erectile function domain entiated well between the two groups. Highly significant [28]. In addition to initial validation in clinical and non- differences were observed on all six domains between the clinical samples, the IIEF has recently been validated patients and controls, indicating that the measure is very against patient’s self-assessments of erectile function in sensitive in differentiating responses between sexually clinical trials of ED [29]. dysfunctional and nondysfunctional women [27•]. The A brief, five-item version of the test has also been Female Sexual Function Index is easy to administer and shown to be useful for screening of patients in clinical score and is currently being used in a number of clinical settings [30]. Psychometric validation has demonstrated a trials of female sexual dysfunction. high degree of reliability (internal consistency and test- retest reliability) in both clinical and nonclinical samples. Brief Sexual Function Index for Women Discriminant and concurrent validity are adequate. This is a 22-item, multidimensional self report instrument Sensitivity and specificity (treatment responsiveness) are for women that assesses sexual function in seven dimen- excellent, as has been demonstrated in recent clinical trials. sions: sexual thoughts/desires, arousal, frequency of activ- Major advantages of the IIEF are its relative brevity and ity, receptivity/initiation, pleasure/orgasm, relationship ease of use, inclusion of multiple domains of sexual satisfaction, and sexual problems. The scale also yields an function, and strong psychometric profile. At present, overall composite score. The measure was originally the IIEF is widely used as an international gold-standard validated in a normal sample of 225 women aged 22 to 55 in both clinical and research assessment of male years, 187 of whom had regular sexual partners [33]. erectile function. Significant differences were observed on most dimensions of sexual function between women with and without Brief Male Sexual Function Inventory sexual partners. More recently, the scores of the original This is an 11-item questionnaire scale that assesses several validation sample were compared with a clinical sample of components of male sexual function, including sexual 104 women in the same age range who had undergone drive, erection, ejaculation, sexual problems, and overall bilateral oophorectomy and hysterectomy [34]. This study satisfaction [25•]. Major advantages of this scale are: demonstrated significantly lower scores on six of seven 1) a relatively high degree of internal consistency and test- dimensions of sexual function and the overall composite retest reliability, 2) adequate discriminant validity for three scores of women who had undergone oophorectomy of the domains (erectile function, problems, overall compared with controls. In particular, the dimensions of satisfaction), and 3) ease of use. Potential disadvantages sexual desire, arousal, and frequency of activity were the are the restricted evaluation of erectile and orgasmic most significantly different between the two groups. Most function, and lack of evidence concerning sensitivity or recently, this measure was found to be responsive to Measurement of Male and Female Sexual Dysfunction • Rosen 185 testosterone replacement therapy effects in the sample of and patient satisfaction measures as secondary endpoints. women with bilateral oophorectomy [35]. Although these measures provide a potentially broader understanding of treatment effects, several limitations and Derogatis Sexual Function Inventory problems are evident. First, most quality of life scales are The Derogatis Sexual Function Inventory (DSFI) is a designed for use in medically ill patients, whose disease or comprehensive, multidimensional measure of male and treatment has a noticeable impact on physical or psycho- female sexual function [36]. The complete DSFI scale consists logic functioning. Although sexual dysfunction patients of 245 items, requiring 60 minutes or longer to complete. Ten may have deficits in some areas [39], clinical trials typically domains of sexual function are assessed, including informa- exclude patients with major medical or psychiatric disease. tion, experience, drive, attitudes, psychologic symptoms, Additionally, most domains of quality of life assessment, affects, gender role definition, fantasy, body image, and sexual such as physical functioning, cognitive performance, and satisfaction, in addition to a global sexual satisfaction index. global health perceptions, are unlikely to be affected by the The test has been psychometrically validated, and has been symptoms of sexual dysfunction or its treatment. widely used in earlier studies in the 1980s of normal and In response to the need for a more disease-specific dysfunctional individuals. Its major drawbacks are the approach, two new instruments for quality of life assess- excessive length and complexity of the instrument, which ment in erectile dysfunction trials have been developed. make it generally unsuitable for use in clinical trials. However, Wagner et al. [40] report the development of a 19-item the measure remains the most comprehensive assessment scale (QOL-MED) , based on semistructured interviews questionnaire for use in both male and female subject. with a representative sample of patients with ED. This A structured interview form of the DSFI has recently measure has a high degree of reproducibility and internal been published [37•]. Although the structured interview consistency, but has received little validation in ED format offers potential advantages in terms of clinical patients or controls. More recently, Fugl-Meyer et al. [39] validation, the measure has yet to be evaluated in large have described the use of a brief, eight-item life satisfaction scale clinical trials. However, this measure may be of checklist for specific quality of life assessment in ED trials. particular value in assessing response to broader (ie, non- This measure was found to differentiate between patients pharmacologic) approaches to treatment of sexual dys- with ED and controls on several dimensions. Significant function. The structured interview approach can be used improvements on two scale dimensions (sexual life and for assessment of both male and female dysfunction. overall life satisfaction) were found following successful treatment with prostaglandin injections. This measure provides a broad assessment of quality of life dimensions Daily Diaries and Event Logs of potential interest in ED patients. Daily diaries or sexual event logs are alternative measures of A treatment satisfaction measure (Erectile Dysfunction sexual function that may be used to complement the use of Inventory of Treatment Satisfaction [EDITS]) has also self-report questionnaires. Event logs or daily diaries recently been described [41•]. This measure assesses typically include assessment of variables such as intercourse patient and partner ratings of treatment satisfaction across frequency and satisfaction, quality of erection, and medica- several domains of treatment efficacy. The measure has had tion use. The Sexual Encounter Profile (SEP) is a six-item limited psychometric validation and has been used in event log that has recently been used in a number of large- recent clinical trials with sildenafil. scale clinical trials. In a preliminary validation study, a high Despite the availability of the above measures, more degree of correlation was observed between erection and research is needed on treatment-specific quality of life intercourse satisfaction ratings on the SEP and IIEF measures measures for assessing sexual dysfunction outcomes in in patients with mild to moderate degrees of ED [38]. males and females. Similar event logs have been developed for use in clinical trials of female sexual dysfunction, although none of these have been systematically validated to date. Event logs have Conclusions been developed specifically for clinical trial use and are not A variety of measurement approaches are currently recommended for routine clinical use at present. available for assessing male and female sexual dysfunction. Although physiologic measures, such as penile rigidity and tumescence assessment in the male, and vaginal blood flow Quality of Life and Treatment measures in women, have been used in the past, these are Satisfaction Measures less frequently used at present. Rather, a number of recent Quality of life measures, such as physical functioning, self-report measures have been developed for multidimen- mood state, and overall life satisfaction are routinely used sional assessment of sexual function in both men and in large-scale clinical trials of cardiovascular disease, cancer women. Several of these measures have demonstrated and other chronic illnesses. Recent clinical trials of male adequate psychometric properties, including test-retest and female sexual dysfunction have included quality of life reliability, internal consistency and discriminant validity. 186 Sexual Dysfunction

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