In our study, we evaluated the kinetics of inflammatory variables including CRP and PCT in terms of their prognostic power in predicting mortality in patients with nosocomial BSI. The main finding of the study is that ∆PCR is significantly more effective in predicting 28-day mortality than ∆CRP and ∆PCT alone. There are several studies investigating the predictive value of inflammatory indicators such as CRP and PCT in mortality in critically ill patients [5, 8, 26, 27]. According to our knowledge, this is the first article reporting the association between ∆PCR and hospital mortality in patients with nosocomial BSI. Our data suggest that combined assessment of ΔPCT and ΔCRP could increase the predictive value of these parameters. For ∆PCR, it was found that the intersection point of -0.05 is predicting the 28 days mortality by ROC curve. The results of this study make contribution to the literature on the prognostic role of ∆PCR on mortality in critically ill patients.
Timely diagnosis and treatment are required to reduce bacteremia-related morbidity and mortality . Serum PCT and CRP have good clinical diagnosis and prognostic value for patients with sepsis and septic shock. Kinetic studies of PCT and CRP may increase sensitivity and accuracy when evaluating the prognosis of patients with sepsis and septic shock . They have been used for early detection of infection and directing antibiotic therapy . PCT level was higher in patients with nosocomial BSI and was more useful for predicting nosocomial BSI than CRP or white blood cell count . PCT change faster than CRP in response to bacterial infection, and proper antibiotic therapy is associated with a rapid decrease in PCT levels . A systemic review and meta-analysis study showed that PCT levels were significantly different between surviving and non-surviving sepsis patients . The prognostic value of CRP and PCT kinetics has been studied in several types of infection, with mortality as the main outcome variable. Initial CRP and PCT cannot be considered useful markers in patients with acute and chronic conditions . In recent studies, different results have been observed on the relationship of PCT and CRP levels with mortality [30, 31]. CRP and PCT kinetics in the first days were associated with use of appropriate (active) empirical therapy [26, 32]. A large multicenter prospective study showed that the decrease in PCT levels by more than %80 was a predictor of mortality and can be used in managing sepsis . In another prospective study, initial levels of CRP and PCT and their combinations in patients with sepsis, were found to have limited value in predicting 28 days mortality . In our study, we did not find basal (day 1 of BSI) levels of CRP, PCT and PCR significant at 28-day mortality. However, we found the kinetics that reflect the differences between the 5th and 1st days to predict mortality. In particular, PCR kinetics was remarkable in terms of prediction (OR = 36.8). It is thought that PCR kinetics are thought to be superior in predicting mortality due to PCT levels rises and falls earlier than CRP and CRP are affected more by non-infectious diseases than PCT.
Recently, there were reports on the benefit of the PCR in various infectious conditions of adult patients. In a study on the adult pneumonia, log PCR was significantly higher in patients with Legionella pneumonia compared with pneumococcal pneumonia concluding that PCR resulted in excellent discrimination between infections caused by these two pathogens. It was because increase of CRP was more significant than PCT in Legionella pneumonia patients. . Similarly, different increasing patterns of CRP and PCT were found in suspected sepsis group and the proven sepsis group in the present study, which was reflected in the decreased log PCR as well . In addition, Hangai et al. reported that PCR showed best performance in discrimination between tumor fever and infection induced fever in patients with hematological diseases (CRP AUC 0.67, PCT AUC 0.70, and PCR AUC 0.75). These results implicate that PCT and CRP differently respond to various infectious conditions, which makes PCR as a potential tool in differentiation of various infectious diseases . In other study, PCR showed highest AUC compared with CRP and PCT in discrimination of proven sepsis and suspected sepsis in neonates even though there was no statistical difference . In our study, ROC analysis showed that PCT was more useful than CRP in terms of the AUC. Furthermore, ∆PCR was the best test to discriminate between surviving and non-surviving, showing the highest AUC.
Although, there are many scoring systems used to estimate the prognosis of critically ill patients, the ∆PCR is valuable because it is relatively simple and easy to use in all settings. However, there are several limitations of this study. Firstly, it is a retrospective single center study done on a selected population. There may have been some selection bias because of the study’s retrospective design. The patient population might be heterogenous because of various hospitalization settings, including intensive care units. Secondly, PCT and CRP results were reported routinely at our hospital so our clinicians were not blind to the results. This can cause bias and effect the predictive value of PCR. Thirdly, we couldn’t investigate the associations of general mortality because cases without BSIs and nosocomial infections other than BSIs were excluded. Nonetheless, PCR was not used in follow up or making up critical decisions for patients.