Valid symptom reporting at upper endoscopy in a random sample of the Swedish adult general population: the Kalixanda study

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Abstract
Background: Upper oesophagogastroduodenoscopy is considered to be the gold standard for upper gastrointestinal disease assessment, but is currently seldom used in epidemiological studies. One concern is that the procedure may bias sampling among volunteers in a general adult population. The aim of this study was to explore whether the procedure affects symptom reporting. Methods: A random sample of 3000 adults aged 20-81 years (mean age 50.4), from two Swedish municipalities (n = 21,610) was surveyed using a validated postal questionnaire (the Abdominal Symptom Questionnaire) assessing gastrointestinal symptoms. A subsample of the responders was invited, in random order, to undergo an upper endoscopy and repeated symptom reporting using the same questionnaire, as well as a serology test for Helicobacter pylori. Results: The response rate to the initial questionnaire was 74.2% and the participation rate for those eligible for the upper endoscopy was 73.3% (n = 1001, mean age 54.0 years, 48.8% male). No major social or symptom sampling error was encountered from the selection process, with the exception of an excess of symptom reporters among the youngest subjects. The prevalence of reflux symptoms, dyspeptic symptoms and irritable bowel symptoms was 40%, 37.6% and 29.6%, respectively, which is relatively high, but in no way extreme. Conclusions: The upper endoscopy survey strategy was successful. The response rate was high and there was no major selection bias of clinical relevance. The cohort selected for this study appears to be representative of the general Swedish adult population.