In each patient we will calculate the symptom index (SI) for chest pain. Bioview analysis software will be used for the calculation of SI. According to the setting of this software the symptoms will be considered as being related to reflux if they occur within a 2-min time window after the onset of the reflux episode. SI will be defined as the number of symptoms associated with reflux divided by the total number of symptoms. A positive SI is declared if ≥ 50% (i.e, at least half of the symptoms are associated with reflux).