Hs-cTnT Predicts Mortality in Suspected Infection Patients
The main finding of the present study is that the routinely used cardiac biomarker hs-cTnT is an independent predictor of inhospital mortality in ED patients with a suspected infection.
Approximately 5% (10 out of 215, see figure 1) of the ED patients with a suspected infection had an unanticipated transfer from ward to ICU or died on the ward while not having a DNR status, similar as the number that was found by Kennedy et al. The observation that ~33% (2 out of 6) of the ED patients with an unanticipated transfer died in the ICU, versus ~26% of the patients directly admitted to the ICU corresponds to previous studies, and underlines the importance of improving risk stratification of ED sepsis patients.
Conversely, ~32% (13 out of 42, see figure 1) of ED patients with a suspected infection were admitted to the ICU shorter than 24 h, and without specific ICU-related interventions. Although observation is an important function of ICUs, it is likely that these patients would have survived on a normal ward, at much lower costs, which is important because the healthcare-associated costs for sepsis are still increasing. Thus, there is still a need for improvement of risk stratification of ED sepsis patients.
The present study is the first to show that hs-cTnT is an independent predictor of inhospital mortality in ED patients with a suspected infection, with similar accuracy and discriminative power as the MEDS and PIRO scores (figure 3). ED patients with an hs-cTnT in the lowest first quartile (<7 ng/L) could have been safely discharged home directly from the ED with a 100% specificity for survival. ED patients with a hs-cTnT in the fourth quartile (70 ng/L) have a 5.8 times higher odds to die in the hospital compared to patients with a hs-cTnT in the second quartile (11 ng/L), even when initial illness severity and ED treatment is taken into account.
Several studies found troponin to be an independent predictor of mortality in ICU patients with severe sepsis or septic shock, consistent with the present study. However, our findings are in contrast with the study of Rosjo et al and Triuvoipati, who found that hs-cTnT was not an independent predictor of mortality in ICU patients with septic shock. This discrepancy is probably caused by the differences in patient populations and the different troponin assay used. Our ED population contained a much wider severity range of septic patients, including low-risk patients. Patients with septic shock will be easily recognised by the ED physician, and additional risk stratification tools are unlikely to contribute to optimising adequate disposition. Especially in the intermediate risk groups, additional aids in decision making are likely to contribute to optimise initial treatment and safe and cost-effective disposition.
Howell et al proved that PIRO is a valuable concept for risk stratification of ED patients with a suspected infection, but also suggested that it might be fine-tuned by adding biomarkers, or other variables. In the present study, the first necessary step was undertaken to investigate the potential of hs-cTnt for use in risk stratification of ED patients with a suspected infection. Although hs-cTnT is much simpler than the PIRO score and appears to have similar accuracy and discriminative performance, we do not advocate replacement of the PIRO score because PIRO should be used as a classification, with each component giving different information that can be used by the ED physician for decisions for the individual patient. We rather suggest that hs-cTnT could be added to the PIRO score, that is, the organ failure component, if future studies confirm our findings.
In conclusion, the routinely used cardiac biomarker hs-cTnT is associated with illness severity and disposition, and represents an independent predictor of inhospital mortality in ED patients with suspected infection, with similar prognostic performance as the PIRO and MEDS scores. Future studies should confirm whether incorporation of hs-cTnT in the PIRO score increases the prognostic power of the PIRO classification, or whether hs-cTnT might be used as an independent risk stratification tool.
Discussion
The main finding of the present study is that the routinely used cardiac biomarker hs-cTnT is an independent predictor of inhospital mortality in ED patients with a suspected infection.
The Necessity of Improving Risk Stratification of ED Sepsis Patients
Approximately 5% (10 out of 215, see figure 1) of the ED patients with a suspected infection had an unanticipated transfer from ward to ICU or died on the ward while not having a DNR status, similar as the number that was found by Kennedy et al. The observation that ~33% (2 out of 6) of the ED patients with an unanticipated transfer died in the ICU, versus ~26% of the patients directly admitted to the ICU corresponds to previous studies, and underlines the importance of improving risk stratification of ED sepsis patients.
Conversely, ~32% (13 out of 42, see figure 1) of ED patients with a suspected infection were admitted to the ICU shorter than 24 h, and without specific ICU-related interventions. Although observation is an important function of ICUs, it is likely that these patients would have survived on a normal ward, at much lower costs, which is important because the healthcare-associated costs for sepsis are still increasing. Thus, there is still a need for improvement of risk stratification of ED sepsis patients.
The Prognostic Performance of hs-cTnT in ED Sepsis Patients
The present study is the first to show that hs-cTnT is an independent predictor of inhospital mortality in ED patients with a suspected infection, with similar accuracy and discriminative power as the MEDS and PIRO scores (figure 3). ED patients with an hs-cTnT in the lowest first quartile (<7 ng/L) could have been safely discharged home directly from the ED with a 100% specificity for survival. ED patients with a hs-cTnT in the fourth quartile (70 ng/L) have a 5.8 times higher odds to die in the hospital compared to patients with a hs-cTnT in the second quartile (11 ng/L), even when initial illness severity and ED treatment is taken into account.
Several studies found troponin to be an independent predictor of mortality in ICU patients with severe sepsis or septic shock, consistent with the present study. However, our findings are in contrast with the study of Rosjo et al and Triuvoipati, who found that hs-cTnT was not an independent predictor of mortality in ICU patients with septic shock. This discrepancy is probably caused by the differences in patient populations and the different troponin assay used. Our ED population contained a much wider severity range of septic patients, including low-risk patients. Patients with septic shock will be easily recognised by the ED physician, and additional risk stratification tools are unlikely to contribute to optimising adequate disposition. Especially in the intermediate risk groups, additional aids in decision making are likely to contribute to optimise initial treatment and safe and cost-effective disposition.
Additional Value of hs-cTnT to Risk Stratification by PIRO Score
Howell et al proved that PIRO is a valuable concept for risk stratification of ED patients with a suspected infection, but also suggested that it might be fine-tuned by adding biomarkers, or other variables. In the present study, the first necessary step was undertaken to investigate the potential of hs-cTnt for use in risk stratification of ED patients with a suspected infection. Although hs-cTnT is much simpler than the PIRO score and appears to have similar accuracy and discriminative performance, we do not advocate replacement of the PIRO score because PIRO should be used as a classification, with each component giving different information that can be used by the ED physician for decisions for the individual patient. We rather suggest that hs-cTnT could be added to the PIRO score, that is, the organ failure component, if future studies confirm our findings.
In conclusion, the routinely used cardiac biomarker hs-cTnT is associated with illness severity and disposition, and represents an independent predictor of inhospital mortality in ED patients with suspected infection, with similar prognostic performance as the PIRO and MEDS scores. Future studies should confirm whether incorporation of hs-cTnT in the PIRO score increases the prognostic power of the PIRO classification, or whether hs-cTnT might be used as an independent risk stratification tool.
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