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Background Irritable Bowel Syndrome (IBS) is a common condition characterised by pain, distension and altered bowel habit. Evidence suggests functional foods containing probiotics improve gastrointestinal transit, however, data are limited by short follow-up periods and evaluation in selected populations. Methods A multi-centre, randomized, double blind, controlled trial to evaluate the effect of a probiotic vs non-probiotic dairy product on symptoms in IBS with a constipation element (IBS – Constipation or IBS – Mixed profile). Set in 13 general practices within central England. Individuals meeting the ROME III criteria for IBS, aged 18–65 completed a pre-study diary. Eligible individuals were randomized to consume dairy ‘yoghurt’ products which either did or did not contain active probiotics twice daily and to complete a daily diary. Primary outcome was subjective global assessment of symptom relief at week 4. Other outcomes comprised, IBS symptom scores, pain, bloating and flatulence levels, stool frequency, stool consistency, ease of bowel movement and quality of life. Results 179 were randomized (91 active, 88 placebo). 76 (43 active, 33 placebo) completed the study. No significant between group differences existed at 4 weeks (57% active vs 53% placebo, reported adequate relief (p = 0.71)). By week 8, 46% active vs 68% placebo reported adequate relief (p = 0.03). This was sustained at week 12. Conclusions Significant improvements were reported for most outcomes in all trial participants but improvement did not differ by group. This trial does not provide evidence for effectiveness of a probiotic in IBS, in variance with a body of published literature and review conclusions. Differential drop out may however cloud interpretation of data. UK Trial registration ISRCTN78863629

Background Irritable Bowel Syndrome (IBS) is a chronic/common condition that causes a significant effect on the individual (reduced quality of life), society (time lost off work) and health services. Comparison of studies evaluating the management of IBS has been hindered by the lack of a widely adopted validated symptom score. The aim of this study was to develop and validate a disease specific score to measure the symptoms of patients with IBS. Methods A self-administered 14-item symptom questionnaire (based on Rome II criteria) was mailed to 533 persons included in a prevalence study of IBS. The reliability of each underlying dimension identified was measured by Cronbach's α. Validity was assessed by comparing symptom scores with concurrent IBS specific quality of life (QoL) scores. Reproducibility was measured by the test-retest method and responsiveness measured by effect size. Results 379 (71%) questionnaires were returned. The underlying dimensions identified were pain, diarrhoea and constipation. Cronbach's α was 0.74 for pain, 0.90 for diarrhoea and 0.79 for constipation. Pain and diarrhoea dimensions had good external validity (r = -0.3 to -0.6), constipation dimension had moderate external validity (r = -0.2 to -0.3). All dimensions were reproducible (ICCs 0.75 to 0.81). Effect sizes of 0.27 to 0.53 were calculated for those with a reported improvement in symptoms. Conclusion The Birmingham IBS Symptom Questionnaire has been developed and tested. It has been shown to be suitable for self-completion and acceptable to patients. The questionnaire has 3 internal dimensions which have good reliability, external validity and are responsive to a change in health status.