GM diversity and composition before allo-HSCT. (A) Boxplots showing the distribution of alfa diversity estimated with the Shannon index according to patient outcome (alive vs dead). Significant differences in the GM composition at the family (B) and genus (C) level between the higher- and lower-diversity groups. false discovery rate–corrected Wilcoxon rank-sum tests: ∗∗∗P < .001; ∗∗P < .01; ∗P < .05.