Prognostic value of procalcitonin in <Emphasis Type="Italic">Legionella</Emphasis> pneumonia

The diagnostic reliability and prognostic implications of procalcitonin (PCT) (ng/ml) on admission in patients with community-acquired pneumonia (CAP) due to Legionella pneumophila are unknown. We retrospectively analysed PCT values in 29 patients with microbiologically proven Legionella-CAP admitted to the University Hospital Basel, Switzerland, between 2002 and 2007 and compared them to other markers of infection, namely, C-reactive protein (CRP) (mg/l) and leukocyte count (10⁹/l), and two prognostic severity assessment scores (PSI and CURB65). Laboratory analysis demonstrated that PCT values on admission were >0.1 in over 93%, >0.25 in over 86%, and >0.5 in over 82% of patients with Legionella-CAP. Patients with adverse medical outcomes (59%, n = 17) including need for ICU admission (55%, n = 16) and/or inhospital mortality (14%, n = 4) had significantly higher median PCT values on admission (4.27 IQR 2.46–9.48] vs 0.97 IQR 0.29–2.44], p = 0.01), while the PSI (124 IQR 81–147] vs 94 IQR 75–116], p = 0.19), the CURB65 (2 IQR 1–2] vs 1 1–3], p = 0.47), CRP values (282 IQR 218–343], p = 0.28 vs 201 IQR 147–279], p = 0.28), and leukocyte counts (12 IQR 10–21] vs 12 IQR 9–15], p = 0.58) were similar. In receiver operating curves, PCT concentrations on admission had a higher prognostic accuracy to predict adverse outcomes (AUC 0.78 95%CI 0.61–96]) as compared to the PSI (0.64 95%CI 0.43–0.86], p = 0.23), the CURB65 (0.58 95%CI 0.36–0.79], p = 0.21), CRP (0.61 95%CI 0.39–0.84], p = 0.19), and leukocyte count (0.57 95%CI 0.35–0.78], p = 0.12). Kaplan-Meier curves demonstrated that patients with initial PCT values above the optimal cut-off of 1.5 had a significantly higher risk of death and/or ICU admission (log rank p = 0.003) during the hospital stay. In patients with CAP due to Legionella, PCT levels on admission might be an interesting predictor for adverse medical outcomes. Jeannine Haeuptle, Roya Zaborsky, and Rico Fiumefreddo contributed equally to this article.