Irritable Bowel Syndrome and lactose intolerance: the importance of differential diagnosis. A monocentric study

BACKGROUND: Nowadays Irritable Bowel Syndrome (IBS) and Lactose Intolerance (LI) are two very frequent diseases. IBS is a functional disorder, while LI is caused by the inability to digest lactose. LI is often incorrectly diagnosed as IBS. The aim of our study is to identify LI patients among IBS patients, so as to set up a correct therapy. METHODS: We enrolled 259 patients with IBS and we compared them to a control group of 108 patients. All patients underwent H2 Breath-Test (HBT) and two questionnaires regarding the symptoms associated with IBS and LI were administered to the intolerant subjects and one questionnaire to IBS patients with no LI. RESULTS: At the HBT, 79.9% (n = 207) of patients with IBS were positive, while in the control group were positive 25.0% (n = 27) of subjects (p < 0.001). The questionnaires showed, after a month of therapy, a marked improvement in LI symptoms subjects. In addition, there was also a prevalence of more severe symptoms among subjects with IBS and LI than those with IBS and no LI. CONCLUSIONS: We can affirm that most patients with initial diagnosis of IBS are, instead, lactose intolerant. This diagnosis allows us to undertake an adequate therapy so as to improve symptoms and quality of life. Therefore it is important to include LI in the pathologies with which IBS enters into differential diagnosis.