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Synopsis of the Derogatis Interview for Sexual Functioning

Derogatis, Leonard R.

Derogatis Interview For Sexual Functioning (DISF/DISF-SR)

Clinical Psychometric Research Inc,    
1228 Wine Spring Lane, Towson, MD 21204

Instrument Development
	Year Developed: 1987, 1989
	Primary Measurement Constructs: Principal foundation constructs underlying 
effective sexual functioning.

The Derogatis Interview for Sexual Functioning (DISF) is a brief semistructured interview 
designed to provide an estimate of the quality of an individual's current sexual functioning in 
quantitative terms.  The DISF represents quality of current sexual functioning in a 
multidomain format, which to some degree parallels the phases of the sexual response 
cycle (Masters & Johnson, 1966).  The 25 interview items of the DISF are arranged into five 
domains of sexual functioning: I. Sexual Cognition /Fantasy, II. Sexual Arousal, III. Sexual 
Behavior/Experience, IV. Orgasm, V. Sexual Drive/Relationship.  In addition, the DISF Total 
Score is computed, which summarizes quality of sexual functioning across the five primary 
DISF domains.  The DISF interview requires between 15 to 20 minutes to complete, and 
there are distinct gender-keyed versions for men and women.

In addition to the DISF interview, there is a distinct self-report version of the test known as 
the DISF-SR.  The DISF-SR is also composed of 26 items, and was designed to be as 
comparable to the DISF interview as possible.  Time requirements for the DISF-SR are 
similar to the DISF; however, in most contexts the self-report version typically requires a few 
minutes less than the interview.  Time requirements drop noticeably for both versions on 
successive administrations, such as in clinical efficacy or effectiveness trials, where the test 
is administered sequentially.  With slight modifications in format, the DISF-SR may also be 
utilized to gain evaluations of the patient's sexual performance by the patient's spouse.

The DISF and DISF-SR were developed to address the unmet need for a set of brief, 
gender-keyed, multidimensional outcome measures that would represent the status of an 
individual's current sexual functioning, and do so at multiple levels of interpretation.  The 
DISF/DISF-SR are designed to be interpreted at three distinct levels: the discrete item level 
(e.g., "A full erection upon awakening", "Your ability to have an orgasm"), the functional 
domain level (e.g., Sexual Arousal Score), and the global summary level (e.g., DISF/DISF-
SR Total Score).  Since the DISF interview and the DISF-SR self-report inventory are 
matched on an almost item-for-item basis, clinician and patient assessments of the patient's 
quality of sexual functioning may be obtained in both raw and standardized score formats.  
Both instruments may be used repeatedly throughout efficacy or effectiveness trials, or may 
be implemented solely at pre- and post-intervention without significant "practice" effects or 
loss of validity.

Norms and Standardized Scores
Norms have been developed for both the DISF and the DISF/SR, based in each case, on 
several hundred nonpatient community respondents.  The norms are gender-keyed (i.e., 
separate norms for men and women), and are represented as standardized scores in terms 
of Area T-scores.  The Area standardized score possesses distinct advantages over the 
simple Linear transformation, in that the former provides accurate percentile equivalents 
(i.e., T-score of 30= 2nd centile; T-score of 40= 16th centile; T-score of 50= 50th centile; T-
score of 60= 84th centile; T-score of 70= 98th centile, etc.).  This important characteristic is 
not true of Linear T-scores except when the underlying raw score distribution is perfectly 
normal.  In addition to enabling accurate comparisons across respondents, Area T-scores 
also facilitate meaningful comparisons of strengths and weaknesses within a respondent's 
profile of sexual functioning.  A patient may reveal a relatively unremarkable profile with the 
exception of a profound decrement in a single functional domain, or may show a low grade 
degradation of performance across multiple areas of functioning.  Because DISF/DISF-SR 
domain scores are available in an equivalent standardized metric, such evaluations can 
help pinpoint the nature and extent of sexual dysfunctions.

Instrument Type
Clinical/Research Instrument, Interview & Self-Report

Languages Available
Danish, Dutch, English, French, German, Italian, Norwegian, Spanish

Item Format
The DISF/DISF-SR are each comprised of 25 items.  In the case of the former, items are 
cast in the format of a semi-structured interview structured via 4-point Likert scales.  The 
items of the DISF-SR are also represented a 4-point Likert scales, and are designed to the 
extent possible, to match the items of the DISF.

Reliability and Validity Studies
The DISF and DISF-SR have both demonstrated favorable profiles of psychometric 
characteristics (Tables 1-4).  Table 1 provides a summary of several reliability studies on 
the two tests which show both versions of the DISF to be highly reliable.  The interrater 
reliability coefficients shown in Table 1. for the DISF were developed during preliminary 
training sessions for a large, multicenter drug trial in which 16 distinct clinician/raters 
participated.  These data reveal DISF domain coefficients ranged from a low of .84 for 
Orgasm to a high of .92 for Sexual Cognition/Fantasy.  The Interrater coefficient for the 
DISF Total Score was a highly satisfactory .91.  Concerning the DISF-SR, both internal 
consistency and test-retest reliabilities were developed from separate subgroups of the 
normative sample.  Coefficients _ ranged from a low of .74 for Sexual Drive/Relationship to 
a high of .80 for Orgasm, very acceptable values for internal consistency estimates.  
Similarly, test-retest reliability coefficients (based on a 1 week interval) were also good, 
ranging from .80 to .90, with the stability coefficient for the DISF-SR Total Score being .86.

An important validity demonstration for multidimensional or multidomain psychological 
outcome measures, concerns the subtest intercorrelation matrix, and  domain score-total 
score correlation vector.  The pattern of these correlations represents a central 
psychometric characteristic of the test which relates to almost all discernable aspects of 
construct validity (Messick, 1995).  If correlations between dimension scores are high, 
concerns may be raised that operational definitions of the domain constructs are redundant. 
 If domain scores do not correlate at least moderately with the Total score, then the 
possibility exists that the domain constructs (e.g., Sexual Arousal, Orgasm) as operationally 
defined by the test items, are not valid components of the higher-order, more general 
construct (e.g., Quality of Sexual Functioning).  A theoretical optimum would find 
correlations between domains near zero, with each domain score showing a moderately 
high correlation with Total score.  In such an ideal design, each domain would contribute 
independent true variance to the Total Score, with minimum redundancy or overlap.

Subtest intercorrelation matrices are presented for the DISF/DISF-SR based on two normal 
and one sexually dysfunctional sample in Tables 2-4.  As is obvious from these data, in all 
cases the mean interdomain correlation coefficients are relatively low (i.e., .23 to .39), while 
the average domain-total correlations for the three samples range from .60 to .71).  This 
pattern of subtest correlations begins to approach optimal, and strongly confirms that DISF 
domains are contributing relatively independent variance to the DISF Total Score.  

The DISF/DISF-SR have been introduced only recently, and much of the clinical research 
done with the tests has primarily involved corporate-sponsored clinical drug trials.  Although 
preliminary data from these studies indicate that the tests are highly sensitive to sexual 
dysfunction, and to a broad range of therapeutic agents, most of the data are proprietary 
and have not yet been made generally available.  In two studies that have been published, 
(Zinreich, Derogatis, Herpst,, 1990a; 1990b) the DISF was utilized with males suffering 
from prostate cancer about to undergo a course of radiation therapy.  At time of initial 
cancer diagnosis, the DISF was utilized in a logistic regression model as a screen for 
impotence, with detailed clinical evaluation as the ultimate criterion.  In this study, sensitivity 
was found to be 86%, specificity was 80%, and the predictive value of a positive was 86%.  
Subsequent to treatment, patients were assigned to three functional categories on the basis 
of clinical evaluation: a.)totally functional, b.)marginally functional, and c.)impotent.  
Scores on the five domains of the DSFI were significantly different across the three groups, 
with mean DISF Total Scores being 48.2, 21.5 and 14.0 respectively.  In this study, with a 
complex sample of patients, the DISF did a superior job of identifying those individuals who 
were dysfunctional prior to treatment, and validly reflected differences in quality of sexual 
functioning subsequent to therapeutic intervention.

Currently, other studies utilizing the DISF/DISF-SR are in the process of submission and 
review for publication, and several new norms (e.g. geriatric, gay men) are in the process of 
being developed.  

How to Obtain
The DISF and DISF-SR are distributed exclusively by Clinical Psychometric Research Inc., 
1228 Wine Spring Lane, Towson, MD, 21204.  Phone 1-800-245-0277; 1- (410) 321-6165; 
FAX 1-(410) 321-6341.

Copyright Owner
Leonard R. Derogatis, Ph.D.

Principal Citations

Derogatis, L.R. (1996)  Derogatis Interview For Sexual Functioning (DISF/DISF-SR): 
Preliminary Scoring, Procedures & Administration Manual. Baltimore, MD, Clinical 
Psychometric Research.

Zinreich, E. Derogatis, L.R., Herpst, J., Auvil, G., Piantodosi, S. & Order, S.E. (1990). 
Pretreatment evaluation of sexual function in patients with adenocarcinoma of the prostate. 
 International Journal of Radiation Oncology & Biological Physics,19, 1001-1004.

Zinreich, E. Derogatis, L.R., Herpst, J., Auvil, G., Piantodosi, S. & Order, S.E. (1990). Pre 
and posttreatment evaluation of sexual function in patients with adenocarcinoma /of the 
prostate.  International Journal of Radiation Oncology & Biological Physics, 19, 729-732.
1228 Wine Spring Lane, Towson, MD 21204, USA Phone: 1-800-245-0277 Fax: 1-410-321-6341
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