Development and validation of the Celiac Disease Questionnaire (CDQ), a disease-specific health-related quality of life measure for adult patients with celiac disease.

BACKGROUND AND GOALS: To develop and validate a disease-specific instrument for measuring health-related quality of life (HRQOL) in patients with adult celiac disease (CD). STUDY: Based on a Medline search of the literature, responses from 10 CD patients and 4 medical experts items potentially affecting HRQOL in CD were identified. This pool was reduced and pretested by 10 other patients and 4 medical experts constructing a preliminary version of the Celiac Disease Questionnaire (CDQ). In a national survey involving 522 respondents of 1000 CD patients (median age 45 y; 78% female) posted by the German Celiac Society completed a medical and sociodemographic questionnaire, the CDQ, the Short Form Health Survey (SF-36), the Hospital Anxiety and Depression Scale German Version HADS-D and the Giessener Symptom List (GBB 24). Subscales were constructed by a principal factor analysis following predefined criteria and validated with other HRQOL measures. Forty-seven out of one hundred patients answered the CDQ a second time 4 weeks after the first posting for the assessment of test-retest reliability.
RESULTS: The factor analysis suggested 4 domains with 7 items each: emotional and social problems, disease-related worries, and gastrointestinal symptoms. The Cronbach alpha for the subscales ranged from 0.80 to 0.91. Test-retest reliability correlations ranged from 0.45 to 0.89. The correlation coefficients with comparable subscales of other instruments ranged between 0.26 and 0.79. The CDQ discriminated in all subscales patients with CD-associated diseases from patients without CD-associated diseases (P<0.001).
CONCLUSIONS: The CDQ is an instrument suited for future use in clinical and research settings.