Diagnostic value of soluble receptor-binding cancer antigen expressed on SiSo cells and carcinoembryonic antigen in malignant pleural effusion in patients with lung cancer

AIM: The aim of this study was to evaluate the diagnostic value of soluble receptor-binding cancer antigen expressed on SiSo cells (sRCAS1) and carcinoembryonic antigen (CEA) in lung cancer patients with malignant pleural effusion (MPE) and benign pleural effusion (BPE). METHODS: Pleural effusion samples from 118 patients were classified on the basis of diagnosis as MPE (n=60) and BPE (n=58). The concentration of sRCAS1 was determined by enzyme-linked immunosorbent assay. The CEA levels were also determined in all patients. RESULTS: Of 60 MPE patients, 50 had sRCAS1>9.7 U/mL and 54 had CEA>5.5 ng/mL. The concentration of both sRCAS1 and CEA in MPE was significantly higher compared with that in BPE (P<0.01 in both cases). With a cutoff point of 9.7 U/mL, sRCAS1 had a sensitivity of 83.3% and a specificity of 91.4% for differential diagnosis. The combined detection of sRCAS1 and CEA had a sensitivity of 98.3% and a specificity of 96.6% to distinguish MPE from BPE. CONCLUSION: The combined detection of sRCAS1 and CEA may be more valuable in the differential diagnosis between MPE and BPE.