Data analysis
Comparisons of postbiotic preparations using direct and indirect
evidence for efficacy and safety was to be conducted. In trials where
postbiotics were administered at different doses, the main analysis used
the results of the higher dose group to avoid the generation of an
auto-loop. Sensitivity analysis on the dose-response was conducted to
determine if there was a difference in results when used as high- or
low-dose.
STATA 14 software was used for data analysis and synthesis, employing
the frequentist approach using random effects model incorporated in
STATA 14. Heterogeneity of studies was measured quantitatively using the
software Review Manager 5.4.
For studies with missing summary statistics, the study authors were
contacted. If they were unresponsive, the guide for data collection in
section 5.5.8 of the Cochrane Handbook for systematic reviews of
interventions was followed.27 Data from figures
reported in journal articles28 was electronically
extracted using WebPlotDigitizer. Missing means and/or SD were derived
from the available data in the studies following the section on data
extraction for continuous outcomes in the Cochrane Handbook (Higginset al., 2022), the formula derived by Wan et
al., 29 and using MedCalc Comparison of Means
Statistical Software (www.medcalc.org/calc/), as appropriate.
Sensitivity analysis was conducted with studies that reported the
efficacy outcome using SCORAD. Results were reported as mean difference
with 95% CI. This sensitivity analysis was done to facilitate ease of
interpretation of results in the clinical setting since SCORAD has an
established minimal clinically important difference (MCID) at 8.7
points.
Publication bias was to be assessed using comparison-adjusted funnel
plots.