A total of 82 RCTs met inclusion criteria. The majority used Lactobacillusbased
interventions alone or in combination with other genera; strains were poorly
documented. The pooled relative risk in a DerSimonian-Laird random-effects metaanalysis
of 63 RCTs, which included 11 811 participants, indicated a statistically significant
association of probiotic administration with reduction in AAD (relative risk,
0.58; 95% CI, 0.50 to 0.68; P.001; I2, 54%; [risk difference, −0.07; 95% CI, −0.10
to −0.05], [number needed to treat, 13; 95% CI, 10.3 to 19.1]) in trials reporting on
the number of patients with AAD. This result was relatively insensitive to numerous
subgroup analyses. However, there exists significant heterogeneity in pooled results
and the evidence is insufficient to determine whether this association varies systematically
by population, antibiotic characteristic, or probiotic preparation.
because of the administered
organism. When more than 1 active
treatment group was investigated, we
selected the group first mentioned as
the main treatment group.