The value of mesothelin in pleural effusion vs histology by medical thoracoscopy

Pleural effusions (PE) are frequently the presenting symptom of neoplastic disease. Serum mesothelin related peptide (SMRP) is a new biomarker for the diagnosis of mesothelioma. The aim of this study was to investigate the diagnostic significance of mesothelin in PE of unknown origin. Pleural fluid, obtained from 104 patients between March 2008 and October 2009, were compared with histology of pleural biopsy taken during consecutive medical thoracoscopy. We had: 34 PE from mesotheliomas (25 epitheliomorphic, 9 sarcomatoid), 35 from pleural metastasis, 35 from benign diseases. SMRP concentrations was obtained using an ELISA test. SMRP levels in PE were significantly higher in patients with epitheliomorphic mesothelioma (mean ±SD, 46,55 nM ± 44,29) than in patients with sarcomatoid mesothelioma (16.11 nM± 25.02) (p=0.061), pleural metastasis (7.52 nM± 10.77) (p<0.0001), benign diseases (5,82 nM± 8,86) (p<0.0001) and in patients with malignant diseases (22.78 nM± 34.02) (p<0.005) than benign diseases. Using ROC curve analysis, pleural fluid SMRP offered an AUC of 0.767 in its ability to differentiate between mesothelioma and all other diagnosis at a cutoff value of 19.6 nM. The diagnostic sensitivity and specificity of pleural fluid SMPR concetration for distinguishing mesothelioma from other causes of PE, at 19.6 nM, were 58.8% and 97.1%, respectively. Pleural SMRP levels higher than 19.6 nM were observed in 18/25 (72%) patients with epiteliomorphic mesothelioma, in 5/35 (14.3%) with pleural metastasis, in 2/9 (22.2%) with sarcomatoid mesothelioma, 1/35 (2.9%) with benign diseases. SMRP has the potential to add clinically significant information in the work-up of patients with a PE of unknown origin.