Abstract and Introduction
Abstract
Introduction: The intent of this study was to determine whether serum procalcitonin (PCT) levels are associated with prognosis, measured as organ dysfunctions and 28-day mortality, in patients with severe pneumonia.
Methods: This was a multicenter, observational study of critically ill adult patients with pneumonia requiring mechanical ventilation conducted in 10 academic hospitals in Canada, the United States, and Central Europe. PCT was measured daily for 14 days using an immuno-luminometric assay.
Results: We included 175 patients, 57 with community acquired pneumonia (CAP), 61 with ventilator associated pneumonia (VAP) and 57 with hospital acquired pneumonia (HAP). Initial PCT levels were higher in CAP than VAP patients (median (interquartile range: IQR); 2.4 (0.95 to 15.8) vs. 0.7 (0.3 to 2.15), ng/ml, P < 0.001) but not significantly different to HAP (2.2 (0.4 to 8.0) ng/ml). The 28-day ICU mortality rate for all patients was 18.3% with a median ICU length of stay of 16 days (range 1 to 142 days). PCT levels were higher in non-survivors than in survivors. Initial and maximum PCT levels correlated with maximum Sequential Organ Failure Assessment (SOFA) score r = 0.50 (95% CI: 0.38 to 0.61) and r = 0.57 (0.46 to 0.66), respectively. Receiver operating curve (ROC) analysis on discrimination of 28-day mortality showed areas under the curve (AUC) of 0.74, 0.70, and 0.69 for maximum PCT, initial PCT, and Acute Physiology and Chronic Health Evaluation (APACHE) II score, respectively. The optimal cut-off to predict mortality for initial PCT was 1.1 ng/ml (odds ratio: OD 7.0 (95% CI 2.6 to 25.2)) and that for maximum PCT was 7.8 ng/ml (odds ratio 5.7 (95% CI 2.5 to 13.1)).
Conclusions: PCT is associated with the severity of illness in patients with severe pneumonia and appears to be a prognostic marker of morbidity and mortality comparable to the APACHE II score.
Introduction
Respiratory tract infections requiring mechanical ventilation account for the majority of all infections treated in the intensive care unit (ICU) and are associated with prolonged hospital stay and high ICU mortality. The Pneumonia Severity Index (PSI) is commonly used for risk stratification of patients with pneumonia. However, this parameter showed only moderate association with outcome prediction and was judged to be inadequate to guide clinical care.
Numerous studies have evaluated the diagnostic performance of invasive procedures, or of biochemical and molecular markers in blood or bronchoalveolar lavage (BAL) in patients with ventilator-associated pneumonia (VAP), hospital acquired pneumonia (HAP) and community acquired pneumonia (CAP). These methods are difficult to apply to daily clinical practice and none has proved to be predictive of outcome. Furthermore, many aspects in the strategies for diagnosing HAP and VAP especially regarding the importance of invasive procedures are still controversial. Indeed, a recent study revealed that use of invasive procedures for etiological diagnosis of pneumonia varies considerably between European ICUs. This uncertainty is most likely responsible for antibiotic overtreatment observed in this group of patients. Thus, measures to aid the early identification of patients with pneumonia are underdeveloped. Such measures are needed as patients with pneumonia are at high risk of death and would benefit from early adaption of therapy.
Procalcitonin (PCT), a relatively novel marker of infectious processes, has been shown to be associated with the severity of inflammation and prognosis during sepsis and septic shock. In two large studies in the emergency department, low PCT-values were associated with a low risk of death in patients with CAP. Luyt and colleagues reported that PCT levels decreased during the clinical course of VAP but were significantly higher from Day 1 to Day 7 in patients with unfavorable outcomes. The significance of PCT is emphasized by the observation that the course of PCT levels may safely guide antimicrobial therapy in patients with community acquired lower respiratory tract infections and ICU patients with suspected bacterial infections. However, data about the significance of PCT in patients with hospital and ventilator acquired pneumonia requiring intensive care therapy are still limited.
The aim of this multicenter study was to test the hypothesis that serum PCT levels can assist in identifying patients with severe pneumonia who are at increased risk of poor outcome, measured as organ dysfunction and 28-day mortality.