Table 1 . Steps of linguistic validation (the MAPI Protocol) .

Stages	Questionnaire
Forward translation by two independent translators	Forward translation A1 (Persian) and forward translation A2 (Persian)
Merging session (analysis and reconciliation) with presence of translators and the executive manager	Forward translation B
Backward translation by another independent translator	Backward translation (English)
Comparing the main questionnaire with the backward translation by the MAPI Research Institute	Forward translation (Persian) C
Review by physician interested in GERD	Forward translation (Persian) D
Final checking and amendment	Forward translation (Persian) E