Microbiome composition is associated with urinary 3-IS levels. (A) LASSO regression was used to predict 3-IS levels from microbiome compositions in cross-validation. Shown is a scatter plot of predicted vs observed urinary 3-IS/mmol crea concentrations. Both axes are plotted on a logarithmic scale. The Pearson correlation coefficient r is 0.703 (P < .001). (B) Heat map representation of the relative abundance of the 18 predictive OTUs in n = 70 stool specimens. The abundance increases from blue to yellow.