Initial validation of a diagnostic questionnaire for gastroesophageal reflux disease.

OBJECTIVES: Brief, reliable, and valid self-administered questionnaires could facilitate the diagnosis of gastroesophageal reflux disease in primary care. We report the development and validation of such an instrument.
METHODS: Content validity was informed by literature review, expert opinion, and cognitive interviewing of 50 patients resulting in a 22-item survey. For psychometric analyses, primary care patients completed the new questionnaire at enrollment and at intervals ranging from 3 days to 3 wk. Multitrait scaling, test-retest reliability, and responsiveness were assessed. Predictive validity analyses of all scales and items used specialty physician diagnosis as the "gold standard."
RESULTS: Iterative factor analyses yielded three scales of four items each including heartburn, acid regurgitation, and dyspepsia. Multitrait scaling criteria including internal consistency, item interval consistency, and item discrimination were 100% satisfied. Test-retest reliability was high in those reporting stable symptoms. Scale scores significantly changed in those reporting a global change. Regressing specialty physician diagnosis on the three scales revealed significant effects for two scales (heartburn and regurgitation). Combining the two significant scales enhanced the strength of the model. Symptom response to self-directed treatment with nonprescription antisecretory medications was highly predictive of the diagnosis also, although the item demonstrated poor validity and reliability.
CONCLUSIONS: A brief, simple 12-item questionnaire demonstrated validity and reliability and seemed to be responsive to change for reflux and dyspeptic symptoms.