Reliability and validity of the digestive health status instrument in samples of community, primary care, and gastroenterology patients

Aim: We evaluated a previously reported digestive health status instrument in community, primary care, and gastroenterology practice populations. Multiple types of reliability, validity and responsiveness were assessed to determine the performance of the questionnaire. Methods: Study populations included community, primary care and gastroenterology subjects. Psychometric analyses included internal consistency and test-retest reliability, criterion and construct validity, and responsiveness. Results: Acceptable internal consistency was seen on all scales in all three populations. Test-retest reliability was excellent in a speciality population with reflux disease. Criterion validity was demonstrated by strong correlation of reflux scale scores and results on 24-h pH monitoring. Scale scores varied predictably in those receiving gastrointestinal tract imaging and according to diagnosis, indicating construct validity. The reflux scale and pain index were sensitive to change with treatment for reflux disease. Multi-trait scaling analyses from the community sample revealed a structure equivalent to that reported from a primary care sample. Conclusions: The reliability and validity of the digestive health status instrument on multiple measures in multiple settings have been demonstrated. The instrument was responsive to change with treatment for reflux disease. The demonstrated robustness attests to the suitability for future studies and clinical application.