Evaluation of soluble mesothelin-related peptide as a marker additional to cytology for diagnosing malignant pleural mesothelioma effusions.

Abstract

e17533 Background: Detection of soluble mesothelin-related peptide (SMRP) levels in serum has been proposed to help the diagnosis of malignant pleural mesothelioma (MPM). In this study we evaluated the SMRP levels in pleural effusions of MPM (MPM-PE), the clinical importance and usefulness of SMRP detection in MPM-PE and whether it can have an additional value to cytological analysis (Cyt). Methods: We studied 52 MPM-PE, 129 benign PE (B-PE) and 94 non-MPM pleural metastasis PE (Mts-PE). In all PE samples, both cytology and SMRP detection were performed. SMRP levels were estimated by means of the MesoMark ELISA kit (Fujirebio Diagnostic, Malvern, PA). Diagnostic performance parameters were estimated through the ROC analysis, Youden's index was applied to obtain the best cut-off level and the degree of correlation was estimated by Diagnostic Odds Ratio (DOR) and by P-value (P) with Chi-square test. Results: The median SMRP levels were significantly higher in MPM-PE (28.2 nM) than in B-PE (3.2 nM) or Mts-PE (3.8 nM). MPM-PE vs B-PE yielded an AUC of 84.5 (P<0.001) whereas MPM-PE vs Mts-PE yelded an AUC of 79.6 (P<0.001). The cut off level in MPM-PE was estimated in 9.30 nM at which value we established Se=75%, Sp=93% for MPM-PE vs BPE and SP=81% for MPM-PE vs Mts-PE. We found SMRP positive cases (≥ cut off) in 38/52 (73%) MPM-PE, in 9/129 (7%) B-PE (DOR=40, P<0.001) and in 18/94 (19%) Mts-PE (DOR=13, P< 0.001).Cyt was negative in 29/52 (56%) of MPM-PE, among which SMRP was positive in 20/29 (69%) cases. Cyt was positive in 15/52 (29%) of MPM-PE, among which SMRP was negative in 4/15 (27%) cases. Finally, in 8/52 (15%) MPM-PE Cyt diagnosis was suspicious and SMRP was found positive in 7/8 (88%) cases. Conclusions: Our results demonstrate that SMRP levels in PE are significantly higher in MPM-PE than in PE from other pathologies. However the test cannot be alternative to cyt but it may provide additional diagnostic value to Cyt. SMRP detection in MPM-PE can be applied in the workup of patients with a PE of unknown origin.