Prospective clinical testing and experimental validation of the Pediatric Sepsis Biomarker Risk Model

Abstract

Sepsis remains a major public health problem with no major therapeutic advances over the last several decades. The clinical and biological heterogeneity of sepsis have limited success of potential new therapies. Accordingly, there is considerable interest in developing a precision medicine approach to inform more rational development, testing, and targeting of new therapies. We previously developed the Pediatric Sepsis Biomarker Risk Model (PERSEVERE) to estimate mortality risk and proposed its use as a prognostic enrichment tool in sepsis clinical trials; prognostic enrichment selects patients based on mortality risk independent of treatment. Here, we show that PERSEVERE has excellent performance in a diverse cohort of children with septic shock with potential for use as a predictive enrichment strategy; predictive enrichment selects patients based on likely response to treatment. We demonstrate that the PERSEVERE biomarkers are reliably associated with mortality in mice challenged with experimental sepsis, thus providing an opportunity to test precision medicine strategies in the preclinical setting. Using this model, we tested two clinically feasible therapeutic strategies, guided by the PERSEVERE-based enrichment, and found that mice identified as high risk for mortality had a greater bacterial burden and could be rescued by higher doses of antibiotics. The association between higher pathogen burden and higher mortality risk was corroborated among critically ill children with septic shock. This bedside to bench to bedside approach provides proof of principle for PERSEVERE-guided application of precision medicine in sepsis.

Conflict of interest statement

Competing interests: The Cincinnati Children’s Research Foundation and H.R.W. hold U.S. patents for the PERSEVERE biomarkers (PCT/US2013/025223, Multi-Biomarker-Based Outcome Risk Stratification Model for Pediatric Septic Shock; PCT/US13/25221, Multi-Biomarker-Based Outcome Risk Stratification Model for Adult Septic Shock; PCT/US14/67438, Temporal Pediatric Sepsis Biomarker Risk Model; and PCT/US08/06172, Biomarkers for Septic Shock Patients). C.J.L. is named as a co-inventor on the patents. H.R.W. also serves on the scientific advisory boards for Inflammatix, Endpoint Health, and Eccrine Systems Inc. All other authors declare that they have no competing interests.

Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Figures

Fig. 1.. Classification of the test cohort patients according to PERSEVERE II.

All patients (n = 461) are included in the root node at the top of the figure, with the corresponding number of 28-day survivors and nonsurvivors and the respective rates. Patients are subsequently allocated to daughter nodes using a biomarker-based criterion as indicated in the top row of each node. All biomarker data are shown as picograms per milliliter, and platelet data are shown as the number of platelets per microliter. Each daughter node provides the number of survivors and nonsurvivors allocated to that node and the respective rates. Subsequent daughter nodes are generated, ending in terminal nodes (TNs) indicated by magenta (italic font). The terminal nodes are used to assign a baseline mortality risk to a patient classified to a given terminal node. The baseline mortality risk corresponding to each terminal node is indicated in parentheses next to the TN and is derived from the published PERSEVERE II model (9). These baseline mortality risks are used for construction of the AUROC. For calculation of the diagnostic test characteristics, the mortality probability is dichotomized into those who are predicted to survive and those who are predicted to not survive by 28 days. Patients allocated to TN1, TN2, TN5, TN8, and TN9 (mortality risk, 0.000 to 0.019) are classified as predicted survivors. Patients allocated to TN3, TN4, TN6, TN7, TN10, and TN11 are classified as predicted nonsurvivors (mortality risk, 0.167 to 0.571).

Fig. 2.. The 28-day survival curves for patients stratified into three PERSEVERE II–based mortality risk strata.

Patients were grouped into one of three PERSEVERE II–based mortality risk strata: low risk, reflecting patients classified to TN1, TN2, TN5, TN8, or TN9 (mortality risk, 0.000 to 0.019); intermediate risk, reflecting patients classified to TN4 or TN6 (mortality risk, 0.167 to 0.189); and high risk, reflecting patients allocated to TN3, TN7, TN10, or TN11 (mortality risk, 0.300 to 0.571). We then generated 28-day survival curves for patients within each stratum. P < 0.001 for all pairwise comparisons, and log rank test with Holm-Sidak method for multiple comparisons.

Fig. 3.. The PERSEVERE II decision tree after pruning.

TN9, TN10, and TN11 from the PERSEVERE II decision tree (see Fig. 1) were pruned and replaced by new TN9 informed by a GZMB decision rule and highlighted by cyan italics. See the main text for the diagnostic test characteristics of the pruned PERSEVERE II decision tree.

Fig. 4.. The derived mPERSEVERE decision tree.

All mice subjected to CLP (n = 94) are included in the root node at the top of the figure, with the corresponding number of 10-day survivors and nonsurvivors and the respective rates. Mice are subsequently allocated to daughter nodes using a biomarker-based criterion as indicated in the top row of each node. All biomarker data are shown as picograms per milliliter. Each daughter node provides the number of survivors and nonsurvivors allocated to that node and the respective rates. Subsequent daughter nodes are generated, ending in terminal nodes (TNs) indicated by magenta (italic font). The terminal nodes estimate the mortality probability for a mouse classified to a given terminal node, and these values are used to calculate the AUROC. For calculation of diagnostic test characteristics, the mortality probability is dichotomized into mice that are predicted to survive and those that are predicted to not survive by 10 days. Mice allocated to TN1 and TN2 (mortality risk, 0.000) are classified as predicted survivors. Mice allocated to TN3, TN4, and TN5 are classified as predicted nonsurvivors (mortality risk, 0.560 to 0.838).

Fig. 5.. Characterization of experimental mice subjected to CLP and stratified into low and high risk of mortality according to mPERSEVERE.

(A) Lung MPO activity in low-risk (n = 20) versus high-risk (n = 20) mice 24 hours after CLP (*P < 0.05 versus low-risk mice). (B) Serum IL6 concentrations in low-risk (n = 20) versus high-risk mice (n = 20) 24 hours after CLP (*P < 0.05 versus low-risk mice). (C) Log-transformed bacterial colony-forming units (CFU) from the peritoneal cavity of low-risk (n = 20) versus high-risk mice (n = 20) 24 hours after CLP (*P < 0.05 versus low-risk mice). (D) Ten-day survival curves of high-risk mice randomized to placebo (n = 15) or dexamethasone (n = 17) in a blinded manner (P = 0.910, log rank survival). (E) Ten-day survival curves of high-risk mice randomized to standard-dose antibiotics (n = 43) or high-dose antibiotics (n = 39) in a blinded manner (P = 0.040, log rank survival).

Fig. 6.. Estimation of pathogen burden among patients stratified into three PERSEVERE II–based mortality risk strata.

Patients were grouped into one of three PERSEVERE II–based mortality risk strata: low risk (n = 286; mortality risk, 0.000 to 0.019), intermediate risk (n = 106; mortality risk, 0.167 to 0.189), and high risk (n = 69; mortality risk, 0.300 to 0.571). (A) Proportion of patients in each risk stratum having any positive pathogen culture from any normally sterile site (P < 0.05, χ2 test, two degrees of freedom). (B) Among patients with positive cultures, proportion of patients in each risk stratum having a positive blood culture (P < 0.05, χ2 test, two degrees of freedom).