Patients with
pneumonia and parapneumonic effusion (PPE) have elevated mortality and a poor prognosis. The aim of this study was to discover novel
biomarkers to help distinguish between uncomplicated PPE (UPPE) and complicated PPE (CPPE). Using an iTRAQ-based quantitative proteomics, we identified 766
proteins in
pleural effusions from PPE patients. In total, 45 of these
proteins were quantified as upregulated
proteins in CPPE. Four novel upregulated candidates (BPI, NGAL, AZU1, and
calprotectin) were selected and further verified using
enzyme-linked
immunosorbent assays (ELISAs) on 220 patients with
pleural effusions due to different causes. The pleural fluid levels of BPI, NGAL, AZU1, and
calprotectin were significantly elevated in patients with CPPE. Among these four
biomarkers, BPI had the best diagnostic value for CPPE, with an AUC value of 0.966, a sensitivity of 97%, and a specificity of 91.4%. A logistic regression analysis demonstrated a strong association between BPI levels > 10 ng/ml and CPPE (odds ratio = 341.3). Furthermore, the combination of pleural fluid BPI levels with LDH levels improved the sensitivity and specificity to 100% and 91.4%, respectively. Thus, our findings provided a comprehensive effusion
proteome data set for PPE
biomarker discovery and revealed novel
biomarkers for the diagnosis of CPPE.