Assessment of the association between Blastocystis infection and irritable bowel syndrome.

To assess the association between Blastocystis infection and irritable bowel syndrome (IBS) in Thai patients, Phramongkutklao Hospital. A case-control study was conducted at Phramongkutklao Hospital, Bangkok, Thailand during 2007-2008. A total of 126 subjects were enrolled into the study. Sixty-six persons were enrolled in the IBS group and 60 persons were enrolled in the control group. Intestinal parasitic infections were determined using wet preparation and formalin-ethyl acetate concentration. Short-term in vitro culture was performed to detect Blastocystis sp. Additionally, stool specimens were cultured for pathogenic bacteria. Patients' history and physical examination were also recorded. Of 66 IBS patients, 61 (92.4%) had abdominal pain, 50 (78.1%) had diarrhea, and 14 (21.9%) had constipation. In vitro cultivation revealed that 10.0% and 16.7% were positive for Blastocystis sp. in the control and IBS group, respectively. There was no significant difference of the prevalence of Blastocystis infection between these 2 groups (p = 0.203). Blastocystis infection was a common parasitic infection which was predominant in both IBS and control group. The presence of Blastocystis sp. in stool did not imply gastrointestinal symptoms in the IBS patients. Further study of subtype characterization of Blastocystis sp. in a larger sample size of the case-control study might reveal a possible relationship between Blastocystis sp. and IBS patients.