Reproducibility and validity of a postal questionnaire: The abdominal symptom study

OBJECTIVE: To find out whether it is possible to examine abdominal/gastrointestinal symptoms by a postal questionnaire. DESIGN: In the Abdominal Symptom Study a postal questionnaire was sent to a representative sample of adults (n = 1290) on two occasions, one year apart. The questionnaire was sent a third time to a subsample (n = 110), and to another sample (n = 213) who had not seen the questionnaire before. A subsample (n = 150 of the 1290) was subjected to a medical interview and examination. SETTING: The municipality of Osthammar, Sweden. PARTICIPANTS: A sample (9.3%) of all Swedish citizens (20-79 yrs) in the municipality. MAIN OUTCOME MEASURE: Reproducibility and validity of a postal questionnaire. RESULTS: The response rate was 90%. Roughly 50% of the study population reported abdominal symptoms. The reproducibility of the results was satisfactory, as was the validity of the questionnaire evaluated by medical interview and examination. Non-responders did not report more symptoms than responders. CONCLUSION: It is possible to examine abdominal/gastrointestinal symptoms with a postal questionnaire. The questionnaire used in The Abdominal Symptom Study seems to be useful for this purpose.