Validity of the Eating Disorder Examination Questionnaire (EDE-Q) in screening for eating disorders in community samples

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Abstract

In order to examine the concurrent and criterion validity of the questionnaire version of the Eating Disorders Examination (EDE-Q), self-report and interview formats were administered to a community sample of women aged 18–45 (n=208). Correlations between EDE-Q and EDE subscales ranged from 0.68 for Eating Concern to 0.78 for Shape Concern. Scores on the EDE-Q were significantly higher than those of the EDE for all subscales, with the mean difference ranging from 0.25 for Restraint to 0.85 for Shape Concern. Frequency of both objective bulimic episodes (OBEs) and subjective bulimic episodes (SBEs) was significantly correlated between measures. Chance-corrected agreement between EDE-Q and EDE ratings of the presence of OBEs was fair, while that for SBEs was poor. Receiver operating characteristic (ROC) analysis, based on a sample of 13 cases, indicated that a score of 2.3 on the global scale of the EDE-Q in conjunction with the occurrence of any OBEs and/or use of exercise as a means of weight control, yielded optimal validity coefficients (sensitivity=0.83, specificity=0.96, positive predictive value=0.56). A stepwise discriminant function analysis yielded eight EDE-Q items which best distinguished cases from non-cases, including frequency of OBEs, use of exercise as a means of weight control, use of self-induced vomiting, use of laxatives and guilt about eating. The EDE-Q has good concurrent validity and acceptable criterion validity. The measure appears well-suited to use in prospective epidemiological studies.

Introduction

It is generally accepted that assessment of the specific psychopathology of eating-disordered behaviour is best achieved through the administration of a structured or semi-structured interview by clinicians or by trained lay interviewers (Garner, 2002). Frequently, however, constraints on time and resources encourage the use of self-report measures. For example in epidemiological studies of low-prevalence psychiatric disorders, it is usually not possible to conduct interview assessment with the total sample. For this reason the use of a two-phase design, in which interview assessment is conducted only with probable cases identified on the basis of a self-report measure, is often employed in such studies (Dunn, Pickles, Tansella, & Vazquez- Barquero, 1999).

Among self-report measures of eating-disordered behaviour, the Eating Attitudes Test (EAT; Garner & Garfinkel, 1979) has been widely employed as an outcome measure in clinical and research settings. A 26-item version of the original 40-item scale (EAT-26; Garner, Olmsted, Bohr, & Garfinkel, 1982) has also frequently been used to detect probable cases of eating disorders in general population surveys. However, the measure was originally developed to assess the specific behaviours and attitudes of anorexia nervosa (AN) patients, and its validity as a ‘case-finding’ instrument has frequently not been supported (Patton & Szmukler, 1995). An additional shortcoming of the EAT is that an omnibus score is derived at the expense of dimensional information concerning particular symptoms (Anderson & Williamson, 2002). The Eating Disorders Inventory (EDI; Garner, Olmsted, & Polivy, 1983), arguably the most comprehensive self-report measure of eating disorder psychopathology, has also been widely used, but it is too long for use as a screening instrument and it has not been validated for this purpose (Garner, 1991).

In general, the use as case-finding instruments of measures developed for use in clinical samples is problematic, since the characteristics of individuals identified as cases in general population surveys may differ from those of individuals presenting to services. For example, items addressing the occurrence of extreme methods of weight control, such as self-induced vomiting and laxative misuse, may be of limited use in community samples, because the prevalence of such behaviours is much lower (Garfinkel et al., 1995). Similarly, the extreme dietary restriction and very low body weights characteristic of AN patients are rarely encountered in general population surveys (Walters & Kendler, 1995). Instruments such as the EAT may therefore not be expected to perform well in detecting the relatively more common eating disorders, such as BED and partial-syndrome cases of AN and BN (Hay, Marley, & Lemar, 1998).

A promising alternative to the EAT is the self-report version of the Eating Disorders Examination (EDE-Q; Fairburn & Beglin, 1994), a 36-item questionnaire derived from and scored in the same way as the interview schedule (EDE; Fairburn & Cooper, 1993). The EDE is widely regarded as the instrument of choice for the assessment and diagnosis of DSM-IV eating disorders (Garner, 2002). The EDE-Q provides a similarly comprehensive assessment of the specific psychopathology of eating-disordered behaviour in a relatively brief self-report format. Studies of the validity of the EDE-Q have demonstrated a high level of agreement between the EDE-Q and EDE in assessing the core attitudinal features of eating disorder psychopathology in the general population (Fairburn & Beglin, 1994), among female substance abusers (Black & Wilson, 1996), and in clinical samples of both bulimia nervosa (BN) and binge eating disorder (BED) patients (Carter, Aime and Mills, 2001, Wilfley, Schwartz, Spurrell and Fairburn, 1997). Acceptable internal consistency and test–retest reliability have also been demonstrated (Luce & Crowther, 1999). For these reasons, the EDE-Q has increasingly been employed as an outcome measure and as an adjunct to the use of the EDE in descriptive studies (Anderson and Williamson, 2002, Pike, Dohm, Striegel-Moore, Wilfley and Fairburn, 2001).

The validity of the EDE-Q in assessing eating disorder behaviours is less clear. In particular, significant discrepancies between the EDE-Q and the EDE with respect to assessment of binge eating behaviour have been reported in both general population and clinical samples (Black and Wilson, 1996, Carter, Aime and Mills, 2001, Fairburn and Beglin, 1994, Wilfley, Schwartz, Spurrell and Fairburn, 1997). These findings are more likely to reflect the inherent difficulty of assessing binge eating behaviours by self-report rather than a particular failing of the EDE-Q (Meadows, Palmer, Newball, & Kendrick, 1986), but would nevertheless be expected to detract from the validity of the measure as a case-finding instrument. Assessment of the frequency of self-induced vomiting and/or laxative abuse by means of the EDE-Q appears to correspond more closely with frequency established through interview assessment, though in clinical samples the mean number of episodes reported may be higher when assessed with the EDE (Carter, Aime and Mills, 2001, Fairburn and Beglin, 1994).

To date, only Fairburn and Beglin (1994) have examined the validity of the EDE-Q in a general population sample and only concurrent validity, that is, agreement between EDE-Q and EDE scores, was considered in this study. Beglin and Fairburn (1992) demonstrated the predictive validity of a short-form of the EDE-Q, comprising those (nine) items which best discriminated cases of clinically significant eating disorders from non-cases in a community sample of women aged 18–35. The items were: presence or absence and number of days of self-induced vomiting and laxative misuse; frequency of OBEs and of diuretic misuse; preoccupation with food and calories; guilt about eating; and pursuit of thinness. The resulting scale (EDE-S) was found to perform better than the EAT in identifying cases and it has subsequently been employed in some general population surveys (Steinhausen, Winkler and Meier, 1997, Hay, Marley and Lemar, 1998). However, the criterion validity of the EDE-Q has not been established.

In preparation for a two-phase epidemiological study of disability and health service utilization associated with the more commonly occurring eating disorders, we examined the validity of the EDE-Q in the population of interest, namely, women aged 18–45 years. Specific aims of the study were to provide further evidence for the concurrent validity of the EDE-Q, to demonstrate the criterion validity of the EDE-Q, to establish appropriate cut-off points for use in screening general population samples and to replicate the findings of Beglin and Fairburn (1992).

Section snippets

Design and participants

The study was carried out in the Australian Capital Territory (ACT) region of Australia (population 314,000), a highly urbanized region which includes the city of Canberra. Participants were recruited in two phases. At the first phase of the study self-report questionnaires were delivered to a sample of 802 female ACT residents aged 18–45, selected at random from the electoral roll and stratified by age in 5-year bands. The questionnaire included the EDE-Q, socio-demographic information and

Comparison of item and subscale scores

There were 195 subjects for whom complete information was available on both EDE-Q and EDE. Table 2 shows mean scores on each subscale of the EDE-Q and EDE, as well as correlations between subscale scores on the respective measures. Data from Fairburn and Beglin’s (1994) study are given for comparison.

Scores on individual items of the EDE-Q were higher than those of the EDE for all but five items, these being: ‘restraint overeating’, ‘food avoidance’, ‘eating in secret’, ‘importance of weight’

Correspondence between EDE-Q and EDE subscales

The findings of the present study provide further support for self-report assessment of the attitudinal aspects of eating disorder psychopathology. Consistent with the findings of Fairburn and Beglin (1994), scores on EDE-Q and EDE were highly correlated and to a similar degree across the four subscales. Also consistent with previous research, scores on items of the EDE-Q tended to be higher than those of the corresponding EDE items, reflecting the use of more stringent wording in the interview

Acknowledgements

The research was conducted while the first author was in receipt of a Research Training Fellowship from the NSW Institute of Psychiatry.

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