BACKGROUND/AIMS: Despite numerous randomized clinical trials and meta-analyses, there is no increased evidence for the efficacy of probiotics in the treatment of irritable bowel syndrome (IBS). We review this evidence, identify and analyse the reasons for this lack of evidence and propose methodological improvements for future studies. METHODS: Based on a literature search, we identified 56 papers that matched the purpose of our analyses. Twenty-seven studies used multi-species bacterial preparations and 29 used single-strain probiotics. They were analysed regarding patients included, treatment duration, probiotic dosage, and outcome measures. RESULTS: Trials in both groups suffered from heterogeneity with respect to probiotic concentration, duration of treatment, and other methodological issues (crossover design and underpowered studies). This heterogeneity did not allow the application of a meta-analytic approach and a systematic review was therefore performed instead. Multi-strain preparations combined 2 to 8 different bacterial subspecies, mostly lactobacilli or bifidobacteria, and used variable lengths of treatments. Overall, more than 50% of trials presented negative outcomes. The majority of the single-strain probiotic trials employing lactobacilli or Saccharomyces were negative, whereas trials employing bifidobacteria showed positive results. CONCLUSIONS: The heterogeneity of the studies of probiotics in IBS questions the value of meta-analyses. The use of different bacterial strains and different mixtures of these strains, as well as different dosages, are the main contributors to this heterogeneity. Current data provides limited evidence for the efficacy of a small number of single-strain probiotics in IBS (mostly bifidobacteria) and sound studies following strict trial guidelines (Food and Drug Administration and European Medicines Agency guidelines for clinical trials) are needed. We summarised and proposed some methodological issues for future studies in the field.
Humans ; Irritable Bowel Syndrome* ; Outcome Assessment (Health Care) ; Population Characteristics ; Probiotics* ; Saccharomyces

Background/Aims: The inflammatory bowel diseases (IBD), ulcerative colitis (UC), and Crohn’s disease (CD) are chronic diseases mostly affecting young patients. As they are diseases accompanying patients for their entire life, and the quality of life (QUOL) interacts with disease activity, improving QUOL should be one of the main goals of therapy. This study aims to identify factors contributing to good or impaired QUOL. Methods: Questionnaires addressing health-related QUOL and other psychological and social features were positioned on our institutions’ webpage and on the webpage of the largest self-help group for IBD in Germany. Patients were subdivided according to their QUOL score with a cutoff of <60. We used the Short Inflammatory Bowel Disease Questionnaire, the Assessment of the Demand for Additional Psychological Treatment, and the Fear of Progression Questionnaire Short Form. Results: High numbers of patients in both subgroups showed an impaired QUOL (87.34% in UC, 91.08% in CD). Active extraintestinal manifestations, smoking, high fear of progression and high demand for psychotherapy were associated with reduced QUOL. In addition, polypharmacological interventions did not result in a good QUOL, but ostomies are linked to improved QUOL especially in CD patients. Conclusions Scores used in clinical day-to-day-practice mainly focusing on somatic factors do not sufficiently address important aspects concerning QUOL. Most importantly, extraintestinal manifestations show a hitherto underestimated impact on QUOL.