Development and multi-site validation of a new condition-specific quality of life measure for eating disorders

Carol E Adair¹ , Gisele C Marcoux¹ , Brian S Cram¹^,2 , Carol J Ewashen³ , Janet Chafe² , Stephanie E Cassin¹^,7 , Jorge Pinzon⁴^,5 , Joanne L Gusella⁶ , Josie Geller⁵^,7 , Yvette Scattolon⁸ , Patricia Fergusson⁹ , Lisa Styles⁴ and Krista E Brown⁷

¹Departments of Community Health Sciences and Psychiatry, Faculty of Medicine, University of Calgary, Room 124 Health Sciences Centre, 3330 Hospital Dr. NW, Calgary, AB T2N 4N1, Canada

²Calgary Health Region, 10101 Southport Road SW, Calgary, AB, T2W 3N2, Canada

³Faculty of Nursing, University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4, Canada

⁴Children's and Women's Health Centre of British Columbia, 4500 Oak Street, Vancouver, BC, V6H 3N1, Canada

⁵Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada

⁶Dalhousie University, Halifax, Nova Scotia, B3H 3J5, Canada

⁷Providence Health Care, 1081 Burrard Street, Vancouver, BC, V6Z 1Y6, Canada

⁸Capital Health, QEII Health Sciences Centre,1278 Tower Road, Halifax, Nova Scotia, B3H 2Y9, Canada

⁹University of Manitoba, Winnipeg, Manitoba, R3T 2N2, Canada

author email corresponding author email

Health and Quality of Life Outcomes 2007, 5:23doi:10.1186/1477-7525-5-23


Published:	30 April 2007

Abstract

Background

In eating disorders (EDs) treatment, outcome measurement has traditionally focused on symptom reduction rather than functioning or quality of life (QoL). Generic QoL measures lack sensitivity for some diagnoses and many not be responsive in eating disorder patients. This article describes the development and validation of a condition-specific QoL measure for adolescents and adults with eating disorders – the Eating Disorders Quality of Life Scale (EDQLS).

Methods

Multi-source and multi-stage methods were used to develop the EDQLS, with participation of patients with EDs, their family members and ED treatment providers. Sources for domain and item development included 39 articles, 12 patient and 10 treatment provider interviews, and 31 first person narratives from the internet. Four stages of validation and pre-testing involving 17 patients, 10 family members and 18 providers reduced 233 items to 40 items in 12 domains. These items were pilot tested in 41 ED patients.

Results

The final instrument was then validated in a 12 site sample of 171 individuals aged 14–60 with EDs. All items showed good dispersion. The total raw mean score was 110 out of 200 (SD 27.6) with higher scores indicating better QoL. Internal consistency was excellent (Cronbach's alpha = .96) and subscale internal consistency ranged from alpha .36 to .79 providing evidence for a strong overall construct and some multi-dimensionality. Validity was supported by significant differences in mean EDQLS according to severity levels on the EDI-2 (F = 95.3, p <.001) and the BSI (F = 86.9, p <.001). EDQLS scores were positively associated with time in treatment (F = 4.65, p = .01) suggesting responsiveness. A strong positive association was also found between EDQLS scores and stage of change (F = 15.1 p <.001). Pearson's correlations between the EDQLS and criterion instrument scores were .71 for the SF-12 mental subscale, .61 for the QoLI and .78 for the 16D, supporting construct validity. Exploratory principal components and item response theory analyses identified only a few poor fitting items.

Conclusion

The EDQLS has promising psychometric characteristics and may be useful for evaluating ED treatment effectiveness.