Double-blind, randomised controlled trials (RCTs) of probiotics versus placebo for the prevention of antibiotic-associated diarrhoea were eligible for inclusion. Trials had to report on the incidence of diarrhoea in each group. Trials using other anti-diarrhoea medications were excluded.
The included trials studied various probiotics, including bifidobacteria, lactobacilli, enterococci, streptococci, the yeast Saccharomyces boulardii and combinations of these, for a duration ranging from three days to several weeks. The definition of diarrhoea varied across trials, although most trials defined it as a bowel frequency of three or more movements per day. Various antibiotic indications were studied, although some trials specifically focused on the eradication of Helicobacter pylori. The mean age of patients was five years in paediatric trials and 52 years in adult trials. Included trials were published from 1979 to 2011.
The authors did not state how many reviewers undertook study selection.