Diagnostic Accuracy of Pleural Fluid Cytology, Carcinoembryonic Antigen and C-Reactive Protein Together in Patients With Pulmonary Metastases and Malignant Pleural Effusion

Background/Aim: Pleural effusion (PE) has a heterogeneous aetiology, and differential diagnosis between benign and malignant disease may require invasive procedures in up to 60% of cases. The sensitivity of pleural cytology is limited, and several strategies have been tested to reduce the need of invasive diagnostic approaches. The aim of this study was to evaluate the usefulness of pleural fluid cytology, compared to, and combined with, carcinoembryonic antigen (CEA), C reactive protein (CRP), and lactate dehydrogenase (LDH) assay of pleural fluid (PF) in patients with a history of cancer, exudative non-purulent PE, and suspicion of malignant PE on imaging studies. Patients and Methods: The medical records of 40 patients with pulmonary metastases and malignant PE, and 57 controls with benign exudative PE were reviewed. All the patients underwent pleural cytology and CEA, CRP, and LDH assay before VATS-guided biopsy. Results: The sensitivity and specificity were 55.0% and 98.2% (cytology), 35.0% and 98.2% (CEA), 92.5% and 71.9% (CRP), 70.0% and 54.4% (LDH). The multivariate analysis excluded LDH, and the final AUC (cytology+CEA+CRP) was 0.894. Conclusion: In all patients with a history of cancer and PE of uncertain origin, the combination of PF cytology plus pleural CEA and CRP assay together should be suggested to recognize malignant plural effusion (MPE), minimising the use of unnecessary invasive investigations.