Abstract
It is difficult to make a distinction between inflammation and infection. Therefore, new strategies are required to allow accurate detection of infection. Here, we hypothesize that we can distinguish infected from non-infected ICU patients based on dynamic features of serum cytokine concentrations and heart rate time series. Serum cytokine profiles and heart rate time series of 39 patients were available for this study. The serum concentration of ten cytokines were measured using blood sampled every 10 min between 2100 and 0600 hours. Heart rate was recorded every minute. Ten metrics were used to extract features from these time series to obtain an accurate classification of infected patients. The predictive power of the metrics derived from the heart rate time series was investigated using decision tree analysis. Finally, logistic regression methods were used to examine whether classification performance improved with inclusion of features derived from the cytokine time series. The AUC of a decision tree based on two heart rate features was 0.88. The model had good calibration with 0.09 Hosmer–Lemeshow p value. There was no significant additional value of adding static cytokine levels or cytokine time series information to the generated decision tree model. The results suggest that heart rate is a better marker for infection than information captured by cytokine time series when the exact stage of infection is not known. The predictive value of (expensive) biomarkers should always be weighed against the routinely monitored data, and such biomarkers have to demonstrate added value.
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Acknowledgments
This study was funded by the Flemish government agency for Innovation by Science and Technology (IWT, Grant SBO-080040).
Author contributions
TT, GVdB and GM designed the study and interpreted the results. EB and HV performed the blood sampling in patients and healthy volunteers. TH and MB quantified the serum cytokine concentrations. PM and GM performed the infection scoring, and obtained the informed consents from the patients. FG and GM supervised the machine learning analyses. JMA and DB supervised the time series analyses. TT did the data analyses. All authors have read and approved the final manuscript.
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The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.
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The study was approved by the Institutional Ethical Review Board of the University Hospitals Leuven (ML6625).
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Written informed consent was obtained from the patients’ next of kin and from the healthy volunteers.
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Tambuyzer, T., Guiza, F., Boonen, E. et al. Heart rate time series characteristics for early detection of infections in critically ill patients. J Clin Monit Comput 31, 407–415 (2017). https://doi.org/10.1007/s10877-016-9870-4
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DOI: https://doi.org/10.1007/s10877-016-9870-4