Efficacy assessment The main criteria for treatment efficacy are the value of the IBS severity score. The IBS severity score was established from the self-administered questionnaire developed and validated by Francis. The French version was validated by the MAPI Research Institute. This questionnaire includes two items concerning abdominal pain and abdominal bloating (yes/no) and four visual analog scales (1-100) to assess the severity of abdominal pain, bloating, relief after stool, and impact of symptoms on quality of life. The number of days the patient suffered during the last 10 days was also recorded. The responses were used to calculate a quantitative severity score from 0 to 500 used to make a qualitative classification: severity score 75-175 = mild, 175-300 = moderate, > 300 = severe.