Diagnostic Utility of Plasma Procalcitonin for Nosocomial Pneumonia in the Intensive Care Unit Setting

Abstract

Nosocomial pneumonia is a difficult diagnosis to establish in the intensive care unit setting, due to the non-specific nature of the clinical and radiographic findings. Procalcitonin is a circulating biomarker that may become elevated in the presence of bacterial infection. We conducted a prospective single-center cohort study at Barnes-Jewish Hospital, a 1,200-bed urban teaching hospital in St Louis, Missouri. In medical and surgical intensive care unit patients with suspected nosocomial pneumonia we measured plasma procalcitonin with an enzyme-linked fluorescent assay. We evaluated 104 consecutive patients with suspected nosocomial pneumonia, 67 (64%) of whom met our predefined clinical and microbiologic criteria for definite nosocomial pneumonia. Though the mean procalcitonin concentration was greater in the 67 patients with definite nosocomial pneumonia (18.3 ± 99.1 ng/mL, median 0.8 ng/mL, 5th percentile 0.0 ng/mL, 95th percentile 43.1 ng/mL) than in the 12 patients with definite absence of nosocomial pneumonia (1.7 ± 2.0 ng/mL, median 1.0 ng/mL, 5th percentile 0.0 ng/mL, 95th percentile 6.7 ng/mL), this difference was not statistically significant (P = .66). A procalcitonin cutoff value of > 1 ng/mL yielded a diagnostic sensitivity of 50% and a specificity of 49% for definite nosocomial pneumonia. Receiver operating curve and multivariate logistic regression analyses demonstrated that procalcitonin is inferior to clinical variables for diagnosing nosocomial pneumonia. However, compared to patients with an initial procalcitonin > 1 ng/mL, those with lower procalcitonin had fewer total antibiotic days (13.0 ± 10.3 d vs 19.7 ± 12.0 d, P < .001) and fewer antibiotic days for treatment of nosocomial pneumonia (10.0 ± 5.9 d vs 14.7 ± 7.4 d, P < .001). Plasma procalcitonin has minimal diagnostic value for nosocomial pneumonia.