Combined LRTI prediction metric integrating pathogen detection and host gene expression. Combined LRTI prediction metric integrating pathogen detection and host gene expression. (A) Scores per patient for each of the two components of this LRTI rule-out model are projected into a scatterplot (x axis represents the host metric; y axis represents the microbe score). The thresholds optimized for sensitivity in the derivation cohort are indicated in gray dashed line. Each point represents one patient—those that were in the derivation cohort have no fill, and those that were in the validation cohort are filled. Red indicates LRTI+C+M, and blue indicates no-LRTI subjects. (B) LRTI rule-out model results for each patient are shown for both the derivation and validation cohorts, with study subjects shown in rows and metrics in columns. Dark gray indicates a metric exceeded the optimized LRTI threshold; light gray indicates it did not. Dark red indicates the subject was positive for both pathogen-plus-host metrics, and thus was classified as having LRTI. White indicates missing data. Charles Langelier et al. PNAS doi:10.1073/pnas.1809700115 ©2018 by National Academy of Sciences