CRP (C-Reactive-Protein) and Pneumonia Biomarkers Stratification for Selectively Addressing Priorities in Thoracic Emergency Ultrasound in Pneumonia

Chest-X-Rays (CXR), Computerized Tomography (CT) or Thoracic Ultrasound (TUS) provide images deemed consistent with acute lung consolidation and suitable to confirm the diagnosis of community acquired pneumonia (CAP). Patients which may be affected by CAP are many , but diagnosis is not straightforward because we are managing "a disease characterized by educated guesswork" . Comprehensive imaging workup may be not regularly affordable in busy emergency rooms. Point-of-care TUS allows reliable diagnosis of lung consolidation and of pleural effusion. Regretfully, adequate TUS expertise is more warranted than actually available in most medical departments. Even not specifically investigated, a delay or even an impairment of appropriate TUS or CXR evaluation for several patients may occur due to time- or resource-limiting factors.

Clinical clues of lung consolidation are many. Key symptoms are cough, fever, chest pain and dyspnea with tachypnea, while the major physical signs are chest crackles and dullness. Surrogate biomarkers more easily obtainable in emergency facilities are C-reactive-protein (CRP), peripheral non-invasive pulse-oxymetry and neutrophil-to-lymphocyte ratio (NLR) which is an index of systemic inflammation associated also with pneumonia and subsequent outcome.

The aim of this preliminary study is to evaluate if any clue and which biomarker, including NLR, assessed at Emergency Department (ED) triage, is predictive of the subsequent detection of lung consolidation by TUS and/or by CXR.

The minimal groups' size, with and without TUS or CXR lung consolidation, was calculated according to the difference of the averages of neutrophil-to-lymphocyte ratio (NLR) in the reference the study of Yoon et al. Accepting alpha 0.01, for the probability of type 1 error, and power 80% for probability of type 2 error, a minimum sample size of 19 participants in each group (total 38) was required. Student's t-tests assessed the differences of CRP, WBC - white blood cells count - (TLC), neutrophil count (TNC) and NLR, between the groups with TUS and, separately, with CXR lung consolidation.Thereafter, by ROC (receiver operating curve) analysis, a cutoff of NLR, total leucocytes count (TLC), total Neutrophil count (TNC) and of CRP was calculated vs. the optimal reliability for the detection of TUS consolidation; sensitivity, specificity and accuracy (The proportion of all tests that are correct), and relative Odds Ratio (OR) and confidence intervals (CI) of the individual symptoms, and ORs of so defined laboratory assay cut-offs were calculated separately vs. TUS and CXR consolidation.