This study is a part of a prospective international cohort study on the composition of microbiota living in the upper gastrointestinal (GI) tract and its correlations to the patient’s symptoms, their psychological and physical health status in three different populations (JUICE Study). Our study evaluates reliability of the Persian version of a three part questionnaire which will be used in this study.

The English version of the questionnaire was translated to Farsi and then back translated to English. The back-translation was edited and then retranslated to Farsi. The questionnaire consists of three parts; the first part includes demographic data, the second part is EQ-5D questionnaire which is an instrument developed by EuroQol group to measure five dimensions quality of life and the third part is HADS questionnaire (Hospital Anxiety and Depression Scale). By convenience sampling, 22 participants were enrolled. For checking reliability, they were asked to fill in a questionnaire and repeat this two weeks later. Cohen`s Kappa Coefficient or percentage agreement and Bland-Altman plot were used for statistical analysis as appropriate.

: The first six questions were demographic, and completely the same in the test and retest phases. All of the other questions in the first part of the questionnaire had Kappa values above 0.6 for reliability. Percentage agreements were 0.86, 0.54, 0.66 and 0.9 for reliability for the 8th, 12th, 13th and 14th questions respectively. In the second part, which is EQ5D questionnaire, Kappa value of the first and second items equaled 1. Percentage agreements of the three last items were 0.9, 0.63 and 0.72 respectively. For HADS questionnaire percentage agreement averaged 0.63 in reliability phase.

: According to our data, this three part questionnaire has an acceptable reliability to be used as an instrument in Farsi-speaking population for JUICE study.