Development of a digestive health status instrument: tests of scaling assumptions, structure and reliability in a primary care population

Background: The absence of valid and reliable health status measures for fu nctional gastrointestinal illness has limited research and patient care for this common group of disorders, A self-report survey has been developed, Methods: Initial development focused on extensive pretesting of patients, p rimary care physicians and gastroenterologists. The disease-specific portio n included the Rome criteria for dyspepsia subgroups and the Manning and Ro me criteria for irritable bowel syndrome. The Short Form-36 was added. Psyc hometric analyses included techniques of multitrait scaling, scale internal consistency and criterion validation. Results: Six hundred and ninety patients presenting to their primary care p hysician for treatment of heartburn abdominal pain or discomfort completed the 98 question survey, The disease-specific portion revealed five componen ts including reflux, dysmotility, a two-domain bowel dysfunction complex, a nd a pain index. Internal consistency measures demonstrated good to excelle nt reliability. Scaling successes were observed on multitrait scaling. The disease-specific portion was reduced to 34 questions. Criterion validity wa s demonstrated with the correlation of the disease-specific questions to th e SF-36, Conclusions: The psychometric analyses lend credence to the concept of stom ach and bowel symptom subgrouping as proposed by expert consensus. The psyc hometric properties of the five summated disease-specific scales compare fa vourably with standardized health status measures.