LITERATURE REVIEW
CHAPTER 5 DISCUSSION
5.2 THE PILOT VALIDATION
pathology. These correlations serve to emphasise the complex interplay between mind and body that may contribute to an individual becoming vulnerable to eating
disorders.
The three subscales of disordered eating Drive for Thinness, Bulimia and Body Dissatisfaction are also strongly correlated, i.e., an increase in one subscale is accompanied by similar increases in the others.
5.1.5 Proportional differences above cut-off points
The blacks (32%), Asians (27%) and whites (31%) had a high percentage above the cut-off score on Bulimia. As previously discussed, bulimia nervosa appears to be a growing problem across racial groups. As there is increased pressure to achieve and perform, young people are exposed to additional pressures that may appear overwhelming. On the subscale Perfectionism the black (38%) and Asian (32%) groups scored higher relative to the white group. Wassenaar et al. (2000) argued that the high Perfectionism scores may be related to the need for high achievement in order to obtain a university admission following removal of the constraints of the apartheid years. On the Interpersonal Distrust subscale, all three groups: blacks (30%), Asians (35%) and whites (25%) received high scores. On the Maturity Fears subscale, the scores were: blacks (42%) and Asians (42%), which might indicate that the responsibilities facing black and Asian women may be "perceived as more arduous in general than those facing white women in South Africa" (Wassenaar et al., 2000, p.233). These results seem to suggest that bulimia nervosa and the psychological subscales of Perfectionism, Maturity Fears and Interpersonal Distrust are associated, which is consistent with the findings of Garner and Olmstead (1984).
conducting clinical interviews to determine the match between the EDI categories and clinical interviews for the high and low scoring subgroups.
Although we had hoped to have three categories: high, marginal and low scorers the number of cases in each cell was less than five, which is insufficient for statistical analysis (chi-square analysis). The interviews and EDI scores were therefore recoded to form two categories: high and low scorers.
Definition were as follows:
(1) The high category was an EDI score of 60 and above.
Or
One of the first three subscales and two or more on the psychological subscales
Or
More than one of the first three clinical subscales.
(2) Low category is a score of 59 or below Or
None or one of the other eight EDI subscale categories.
The criteria for assessment of eating disorders in the clinical interview were based on the DSM-IV (American Psychiatric Association, 2000) criteria of eating disorders and participants requiring referral, further assessment or follow-up.
Once the EDI questionnaires were coded, the highest 15 and lowest 15 scorers on the EDI were contacted for a clinical interview. The co-investigator went into the
interviews 'blind', in other words not aware of the participants' EDI scores. After conducting the clinical interviews, each participant was categorised as either high or low scorers on the EDI. The match between the EDI and clinical interview was then determined.
5.2.2 Cross tabulation: clinical rating and EDI rating
A cross tabulation comparing the EDI rating and the clinical ratings only partially confirmed our hypothesis that:
That all participants with a high EDI score, irrespective of their cultural background, correlated with a positive diagnosis for an eating disorder in the clinical interview.
The results indicated a 100% match between the low scorers on the EDI and the low scorers on the clinical interview. This means that the interviewer was able to
correctly diagnose those individuals who did not have any eating pathology or that the EDI was able to identify those individuals who did not have any eating pathology.
There was a 64% match between the high scorers on the EDI and high scorers on the clinical interview. This means that the interviewer was only able to correctly
diagnose those candidates who had eating disorders 64% of the time, or that the EDI was not accurately identifying eating disordered individuals. The overall results indicated that there is an 82% match between EDI ratings and clinical interviews. The error rate was highest for Asian participants (28.6% error rate) and lowest for white participants (6.6% error rate) which suggests that agreement between the clinical interview and EDI is greatest for white high EDI scorers and lowest for Asian high EDI scorers. (The five incorrectly matched participants have been discussed in detail in section 4.3.1.2. of the previous chapter).
A number of statistical tests were performed to determine the significance of the relationship of the EDI rating and clinical interview.
The chi-square test was performed to determine the significance of the relationship of the EDI rating and the clinical rating. There did appear to be a significant match between the two at an alpha level of 0.05, which suggests that we can be 95% certain that the relationship was not obtained by chance. There was a high correlation
between the observed values and expected values as discussed in the previous chapter. Kendall's tau revealed a strong association between the clinical rating and the EDI rating. They were highly correlated and well matched (see Section 4.2.3.).
The above statistical tests suggest that the EDI and clinical interviews can confidently be use in combination as there is a strong correlation between them. The two
instruments used together are a viable research design for a large-scale validation study across ethnic groups.