Biomarkers in pediatric community-acquired pneumonia

Background: Aim of this study was to evaluate the predictive capacity of soluble triggering receptor expressed on myeloid cells-1 (sTREM-1), midregional proatrial natriuretic peptide (MR-proANP) and midregional proadrenomedullin (MR-proADM) in a group of children hospitalized for radiologically confirmed community-acquired pneumonia (CAP). Methods: White blood cell counts, neutrophil percentages and serum C reactive protein (CRP) levels were determined using routine methods. sTREM-1 concentrations were measured using an ELISA; MR-proADM, MR-proANP and procalcitonin (PCT) were measured with an automated immunofluorescent assay. Viral DNA or RNA was extracted using a Nuclisens EasyMAG automated extraction system and tested using the Luminex x TAG Respiratory Virus Panel Fast Assay. To detect pneumococcal cases, nucleic acid extracts from blood and swab samples were tested for two genes of Streptococcus pneumoniae using real-time PCR. Mycoplasma pneumoniae was detected with nested PCR. Results: A total of 433 children with radiologically confirmed CAP were enrolled. CAP was ascribed to bacteria in 235 (54.3%) children and to one or more viruses in 111 (25.6%). CRP and PCT had the best performances for both bacterial and viral CAP identification. The cut-off values with the highest combined sensitivity and specificity for the identification of bacterial and viral infections using CRP were ≥7.98 mg/L and ≤7.5 mg/L, respectively. When PCT was considered, the cut-off values with the highest combined sensitivity and specificity were ≥0.188 ng/mL for bacterial CAP and ≤0.07 ng/mL for viral CAP. For the identification of severe cases, the best results were obtained with evaluations of PCT and MR-proANP. However, in both cases, the biomarker cut-off with the highest combined sensitivity and specificity (≥0.093 ng/mL for PCT and ≥33.8 pmol/L for proANP) had a relatively good sensitivity (higher than 70%) but a limited specificity (of approximately 55%). Conclusion: In children with CAP, sTREM-1, MR-proANP, and MR-proADM blood levels have poor abilities to differentiate bacterial from viral diseases or to identify severe cases, whereas PCT represents the most important biomarker at this regard.