Usefulness of procalcitonin levels in community-acquired pneumonia according to the patients outcome research team pneumonia severity index

Study objectives To evaluate the usefulness of procalcitonin serum levels as a predictor of etiology and prognosis in adult patients with community-acquired pneumonia (CAP) when they are stratified according to severity. Design One-year, population-based, prospective study. Setting University teaching hospital. Patients All adult patients who received a diagnosis of CAP throughout the study period. Interventions and measurements An extensive noninvasive microbiological workup was performed. In patients who gave informed consent, a blood sample was collected at the time the diagnosis of CAP was established to measure biological markers. Procalcitonin levels were measured by a commercially available monoclonal immunoluminometric assay (limit of detection, 0.1 μg/L). Patients were classified according to microbial diagnosis, Patients Outcome Research Team pneumonia severity index (PSI), and outcome measures, and procalcitonin levels were compared among groups. Results Of 240 patients who received a diagnosis of CAP during the study period, procalcitonin concentrations were measured in 185 patients (77.1%). Levels were higher in patients with high-severity risk classes (PSI classes III-V) [p = 0.01] and in those with complications (p = 0.03) or death (p Conclusions Procalcitonin contribution to the evaluation of CAP varies according to severity. While procalcitonin may have a role to predict the microbial etiology in patients with a low PSI score, in patients classified within high PSI risk classes, it is a prognostic marker rather than a predictor of etiology.