Development of diabetes-specific quality of life module to be in conjunction with the World Health Organization quality of life scale brief version (WHOQOL-bREF)

Abstract

Background: Although numerous health-related quality of life (HRQoL) instruments are available for patients with diabetes, the length of these measures may limit their feasibility to routine practice. Also, these measures do not distinguish items for generic and diabetes-specific HRQoL. This study was aimed to develop a diabetes-specific quality of life questionnaire module (DMQoL) to be in conjunction with the World Health Organization Quality of Life scale brief version (WHOQOL-BREF). Methods: One hundred seventeen patients with diabetes were enrolled from a medical center in Taiwan. The item content of DMQoL was constructed based on an extensive review of existing HRQoL instruments for diabetes, expert discussions and patient interviews. A series of psychometric tests were conducted to ensure the reliability and validity of DMQoL. The WHOQOL-BREF served as an existing HRQoL measure for construct validity testing. The response scale of DMQoL was adopted from the 5-point Likert scale of WHOQOL-BREF. Results: A total of 10 items without ceiling or floor effects were selected from 20 items. Exploratory factor analysis (EFA) with parallel analysis and Rasch analysis concluded that the 10 items were embedded in the same underlying concept. The corrected item-total correlations and factor loadings from EFA were all above 0.4. The internal consistency of the 10 items was satisfactory (Cronbach's a = 0.84). The DMQoL total score was moderately correlated with that of WHOQOL-BREF (r = 0.48, p < 0.001). The known-group validity showed that patients with HbA1c <= 7% had significantly higher mean scores of DMQoL than did those with HbA1c > 8% (3.66 +/- 0.47 vs. 3.41 +/- 0.53; p = 0.037). Conclusions: The DMQoL with only 10 items is developed and it is sensitive to the change of diabetes progression in early phases (e.g., glycemic changes). The combination of WHOQOL-BREF and DMQoL provides a comprehensive picture of overall HRQoL in patients with diabetes and enhance the instrument's ability to detect clinically meaningful changes in diabetes.