FSSG (Frequency Scale for the Symptoms of GERD) and questionnaire used in the study. For FSSG, the answer of symptom frequency is from 0 to 4 on each question as follows: never = 0; occasionally = 1; sometimes = 2; often = 3; and always = 4. For the questionnaire on symptoms, medical/family histories, and lifestyles, the answer is "Yes" or "No" for each question.
Yamamichi et al. BMC Medicine 2012 10:45 doi:10.1186/1741-7015-10-45