Diagnostic utility of LUNX mRNA and VEGF mRNA in pleural fluid for differentiating benign from malignant origin.

OBJECTIVE: The purpose of this study was to evaluate the diagnostic utility of lung-specific X protein (LUNX) mRNA and vascular endothelial growth factor mRNA in differentiating pleural effusion of different origin. METHODS: A total of 136 patients with pleural effusion (46 cases of malignant pleural effusion caused by lung cancer, 30 cases of malignant pleural effusion caused by other cancers and 60 cases of benign pleural effusion) were enrolled in this study. Levels of LUNX mRNA and vascular endothelial growth factor mRNA in pleural fluid were detected by real-time quantitative polymerase chain reaction. Pleural fluid carcinoembryonic antigen and Cyfra21-1 were also measured simultaneously. RESULTS: The LUNX mRNA level was significantly higher in malignant pleural effusion caused by lung cancer than in malignant pleural effusion caused by other cancers and in benign pleural effusion. In malignant pleural effusion caused by cancers of different origin, the vascular endothelial growth factor mRNA level was significantly higher than in benign pleural effusion. For the diagnosis of malignant pleural effusion caused by lung cancer, LUNX mRNA exhibited higher sensitivity (80%), when compared with vascular endothelial growth factor mRNA (65%), carcinoembryonic antigen (67%) and Cyfra21-1 (61%), with the same specificity (95%). The combination of LUNX mRNA and cytology achieved a sensitivity of 85%. The combined use of LUNX mRNA and vascular endothelial growth factor mRNA and cytology raised the sensitivity to 89%, with 95% specificity. In initial cytology-negative pleural effusion from lung cancer, LUNX mRNA achieved the highest positive result (65%) among the four markers. CONCLUSIONS: The detection of LUNX mRNA and vascular endothelial growth factor mRNA in pleural fluid may be a complementary tool for the diagnosis of malignant pleural effusion. In particular, pleural fluid LUNX mRNA provided a valuable adjunct in distinguishing malignant pleural effusion caused by lung cancer from benign pleural effusion.