• Rosario Menéndez, José Miguel Sahuquillo-Arce, Soledad Reyes, Raquel Martínez, Eva Polverino, Catia Cillóniz, Juan Ginés Córdoba, Beatriz Montull, and Antoni Torres.
• Servicio de Neumología, Hospital Universitari i Politècnic La Fe, Valencia, Spain. Electronic address: rosmenend@gmail.com.
• Chest. 2012 Jun 1; 141 (6): 1537-1545.

BackgroundThe inflammatory response in community-acquired pneumonia (CAP) depends on the host and on the challenge of the causal microorganism. Here, we analyze the patterns of inflammatory cytokines, procalcitonin (PCT), and C-reactive protein (CRP) in order to determine their diagnostic value.MethodsThis was a prospective study of 658 patients admitted with CAP. PCT and CRP were analyzed by immunoluminometric and immunoturbidimetric assays. Cytokines (tumor necrosis factor-α [TNF-α], IL-1β, IL-6, IL-8, and IL-10) were measured using enzyme immunoassay.ResultsThe lowest medians of CRP, PCT, TNF-α, and IL-6 were found in CAP of unknown cause, and the highest were found in patients with positive blood cultures. Different cytokine profiles and biomarkers were found depending on cause: atypical bacteria (lower PCT and IL-6), viruses (lower PCT and higher IL-10), Enterobacteriaceae (higher IL-8), Streptococcus pneumoniae (high PCT), and Legionella pneumophila (higher CRP and TNF-α). PCT ≥ 0.36 mg/dL to predict positive blood cultures showed sensitivity of 85%, specificity of 42%, and negative predictive value (NPV) of 98%, whereas a cutoff of ≤ 0.5 mg/dL to predict viruses or atypicals vs bacteria showed sensitivity of 89%/81%, specificity of 68%/68%, positive predictive value of 12%/22%, and NPV of 99%/97%. In a multivariate Euclidean distance model, the lowest inflammatory expression was found in unknown cause and the highest was found in L pneumophila, S pneumoniae, and Enterobacteriaceae. Atypical bacteria exhibit an inflammatory pattern closer to that of viruses.ConclusionsDifferent inflammatory patterns elicited by different microorganisms may provide a useful tool for diagnosis. Recognizing these patterns provides additional information that may facilitate a broader understanding of host inflammatory response to microorganisms.

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