Diagnosing pleural effusions using mass spectrometry-based multiplexed targeted proteomics quantitating mid- to high-abundance markers of cancer, infection/inflammation and tuberculosis

Pleural effusion (PE) is excess fluid that appears in the pleural cavity of many lung cancer patients, as well as in those suffering from other ailments like extra-pulmonary tuberculosis (TB) and pneumonia, or stems from a variety of more benign diseases. Diagnosing the cause of the PE is often a clinical challenge and we have applied targeted proteomic methods with the aim of aiding the determination of PE etiology. We developed a mass spectrometry (MS)-based multiple reaction monitoring (MRM)-protein-panel assay to precisely quantitate 53 established cancer-markers, TB-markers, and infection/inflammation-markers currently assessed individually in the clinic, as well as potential biomarkers suggested in the research literature for PE classification. Since MS-based targeted proteomic assays are on the cusp of entering clinical use, we assessed the merits of such an approach and this marker panel in classifying PEs based on a single-center 209 patient cohort with established etiology. We observed groups of infection/inflammation markers (ADA2, WARS, CXCL10, S100A9, VIM, APCS, LGALS1, CRP, MMP9, and LDHA) that specifically discriminate TB-PEs and other-infectious-PEs, and a number of cancer markers (CDH1, MUC1/CA-15-3, THBS4, MSLN, HPX, SVEP1, SPINT1, CK-18, and CK-8) that discriminate cancerous-PEs. Some previously suggested potential biomarkers did not show any significance. Using a Decision Tree/Multiclass classification method, we show a very good discrimination ability for classifying PEs into one of four PE types:
AUC of 0.863 for cancerous-PEs, AUC of 0.859 for tuberculous-PEs, AUC of 0.863 for other-infectious-PEs, and AUC of 0.842 for benign-PEs. Such multiplexed MS assays and the indicated markers show future potential in aiding clinical diagnosis after standard imaging techniques and thoracentesis to help in the hard decision on therapy guidance.