The Domestic/International Gastroenterology Surveillance Study (DIGEST): design, subjects and methods.Scand J Gastroenterol Suppl 1999; 231:9-14SJ
The Domestic/International Gastroenterology Surveillance Study (DIGEST) was designed to examine the 3-month prevalence of upper gastrointestinal (GI) symptoms internationally and the impact of these symptoms on healthcare usage and quality of life.
The study sample was derived from the urban, adult (> or = 18 years) population of Canada, Italy, Japan, The Netherlands, Switzerland, the USA and the Nordic countries (Denmark, Finland, Norway and Sweden). Subjects were randomly recruited on a house-to-house basis in all countries except the USA and Italy, where telephone recruitment was carried out. Participants were interviewed in their own homes (house-to-house recruitment) or at a central location (telephone recruitment). The DIGEST questionnaire consisted of two sections. The first was a newly developed questionnaire consisting of 27 questions examining the prevalence, frequency and severity of upper GI symptoms, and their impact on healthcare use and daily activities. It also examined a number of demographic and socioeconomic variables. This part of the questionnaire was evaluated and pilot-tested before commencement of the survey. The second part of the questionnaire consisted of the local language version of the Psychological General Well-Being Index (PGWBI), a validated generic quality-of-life scale. Following completion of the survey, subjects with upper GI symptoms were classified on the basis of their most bothersome symptom into three symptom groups: gastro-oesophageal reflux-like, ulcer-like or dysmotility-like.
Rigorous design, standardization of interview techniques and prior evaluation of the DIGEST questionnaire, provided a firm foundation for reliable data collection, analysis and interpretation.