Unraveling the ties between irritable bowel syndrome and intestinal microbiota

Table 3 Systemic reviews for randomized controlled trials of probiotics in irritable bowel syndrome

Ref.	Selection criteria	n of identified studies	Results
McFarland et al[73] 2008	RCTs in humans published as full articles or meeting abstracts in peer-reviewed journals	20 RCTs	Global IBS symptoms: RR = 0.77 (95%CI: 0.62-0.94)/ abdominal pain: RR = 0.78 (95%CI: 0.69-0.88)
Brenner et al[76] 2009	RCTs; adults with IBS defined by Manning or Rome II criteria; single or combination probiotic vs placebo; improvement in IBS symptoms and/or decrease in frequency of adverse events reported	16 RCTs → 11 studies showed suboptimal study design	Bifidobacterium infantis 35624 has shown efficacy for improvement of IBS symptoms. Most RCTs about the utility of probiotics in IBS have not used an appropriate study design
Hoveyda et al[74] 2009	RCTs compared the effects of any probiotic therapy with placebo in patients with IBS	14 RCTs → 7 RCTs providing outcomes as dichotomous variable and 6 RCTs providing outcomes as continuous variable	Overall symptoms: dichtomous data - OR = 0.63 (95%CI: 0.45-0.83)/continuous data - mean ± SD, 0.23 (95%CI: 0.07-0.38) Trials varied in relation to the length of treatment (4-26 wk), dose, organisms and strengths of probiotics used
Moayyedi et al[75] 2010	RCTs comparing the effect of probiotics with placebo or no treatment in adult patients with IBS (over the age of 16 yr)	19 RCTs → 10 RCTs providing outcomes as a dichotomous variable	Probiotics appear to be efficacious in IBS (Probiotics were statistically significantly better than placebo, but there was statistically significant heterogeneity). The magnitude of benefit and the most effective species and strain are uncertain
Ortiz-Lucas et al[77] 2013	RCTs comparing probiotics with placebo in treating IBS symptoms	24 RCTs → 10 RCTs providing continuous data performed with continuous data summarized using mean ± SD and 95%CIs	Pain scores: improved by probiotics containing Bifidobacterium breve, Bifidobacterium longum, or Lactobacillus acidophilus species Distension scores: improved by probiotics containing B. breve, B. infantis, Lactobacillus casei, or Lactobacillus plantarum species Flatulence: improved by probiotics containing B. breve, B. infantis, L. casei, L. plantarum, B. longum, L. acidophilus, Lactobacillus bulgaricus, and Streptococcus salivarius ssp. thermophilus

IBS: Irritable bowel syndrome; RCT: Randomized controlled trial.