Mesothelin in serum and pleural effusion in the diagnosis of malignant pleural mesothelioma with non-positive cytology

Mesothelin (SMRP) is regarded as a biomarker of malignant pleural mesothelioma (MPM). Herein, we analyzed the contribution of SMRP detection in pleural effusion and in serum to the diagnosis of MPM with non-positive cytology.The present study included 52 cases of MPM, 43 of pleural benign lesions and 25 of non-MPM pleural metastases. SMRP was measured by MesoMark ELISA (Cis-Bio International Gif/Yvette; France).In non-positive cytology, effusion-SMRP showed higher diagnostic performance than serum-SMRP. We found 38 out of 52 (73.1%) cases of non-positive cytology MPM, out of which 27 (71.0%) were positive for effusion-SMRP (cut-off=12.70 nM) and 18 (47.4%) for serum-SMRP (cut-off=1.08 nM). When cytology, effusion- and serum-SMRP were used in combination, an overall sensitivity in detection of MPM of 78.9% was achieved. The same sensitivity was obtained by combining cytology with effusion-SMRP alone, whereas the combination of serum-SMRP with cytology led to a sensitivity of 61.5%.Detection of both effusion- and serum-SMRP can contribute to improve the diagnosis of MPM with non-positive cytology. However, the analysis of SMRP in effusion makes it unnecessary to test SMRP in the serum.