Abstract
More efficacious tools to distinguish pneumonia from other acute lower respiratory tract infections (OALRTI) in facilities where radiologic studies are not easily or rapidly available are desirable to select the patients who should undergo chest radiographs, to avoid unnecessary visits to the emergency wards of hospitals and to optimize health resources. To this end we analyzed the relevance of many clinical and laboratory parameters, including acute-phase reactants and immune activation markers, in 98 patients with pneumonia and 149 with OALRTI seen at the emergency ward of our hospital. Many clinical and laboratory parameters were associated with the diagnosis of pneumonia in the univariate analysis. Among them, C-reactive protein proved to be the most discriminant for the differentiation between the two conditions (area under the ROC curve 0.83, 95%CI 0.78-0.89, P<0.0001). A multivariate logistic regression analysis revealed that C-reactive protein, presence of suggestive auscultatory findings, lower age, presence of pleuritic pain and lower percent of eosinophils were independently associated with the diagnosis of pneumonia. A formula was derived from this analysis, which, for the most discriminant cut-off level, correctly classified pneumonic and non-pneumonic patients with a sensitivity of 88% and specificity 90%. The area under the ROC curve of this predictive model was 0.93 (95% CI 0.89-0.96, P<0.0001). C-reactive protein, especially if combined with other easily obtained parameters, constitutes a useful adjunct for the differentiation of pneumonia from OALRTI. Routine measurement of these parameters could result in a more adequate utilization of resources.
Highlights
Many patients with community-acquired lower respiratory tract infections are unnecessarily seen in the emergency wards of hospitals, mainly in the winter months, which generate overload, increased health expenditures and inconveniences for the patients
C-reactive protein (CRP), an acute-phase reactant primarily synthesized by hepatocytes as a response mainly to interleukin-6, markedly increases with acute invasive infections paralleling the severity of inflammation or tissue injury[5]
CRP has been identified in respiratory secretions, where it may contribute to bacterial clearance[7,8] and its determination has been considered useful for the diagnosis and management of pneumonia[1,3,9,10]
Summary
Many patients with community-acquired lower respiratory tract infections are unnecessarily seen in the emergency wards of hospitals, mainly in the winter months, which generate overload, increased health expenditures and inconveniences for the patients. Increased levels of this protein have been found in a variety of infectious, inflammatory and neoplastic conditions[22,23,24,25,26] and it has been marginally evaluated in some studies dealing with a reduced number of patients with lower respiratory tract infections[26,27,28] The aim of this prospective study was analyze the behavior of these acute-phase reactants and immune activation markers, as well as many other basic clinical and laboratory parameters, in patients with pneumonia and other acute lower respiratory tract infections (OALRTI) at the time of presentation to the emergency ward of our hospital. From this information we try to derive rules and to define the usefulness of these parameters for the differential diagnosis of both infections, which could help to a better classification of patients and to prevent unnecessary radiographic studies, sparing costs and optimizing emergency ward resources
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