Accuracy of pleural carcinoembryonic antigen (CEA) assay in malignant pleural effusions

Pleural effusion (PE) still represents a challenging diagnostic problem. Although repeated thoracenteses can increase the sensitivity of cytology, it ranges from 50% to 70%. Thoracoscopy can determine the diagnosis, but may be not available or too invasive for patients with poor performance. Several tumor markers or biochemical parameters in pleural fluid have been studied to distinguish between malignant (MPE) and benign PE, but the results were unclear. Furthermore, routine determination of a panel of tumor markers is not cost-effective and cannot be recommended. The aim of our study was to evaluate the accuracy of pleural CEA (pCEA) assay in diagnosing MPE. Pleural effusion samples were collected from 134 consecutive patients (83 males and 51 females, mean age 68.6±11.4 years) with PE, who underwent videoassisted thoracoscopic (VATS) thoracentesis and biopsy, and then VATS or open pulmonary resection. Pleural CEA was measured with automated method of immune-chemiluminescence (LOCI, Dimension Vista, Siemens HD, Camberly, UK), without any pre-treatment of the sample. The cut-off used was 5 ng/mL. Glucose, proteins and LDH serum levels were also assayed. The final histopathology showed 37 (27.6%) non-small cell lung carcinomas (NSCLC), 19 (14.2%) mesotheliomas, 34 (25.4%) metastases (Ms) and 44 (32.8%) benign lesions. Overall, the sensitivity of cytology was 54.4%. The pCEA was positive in 36 out of 37 (97.3%) of patients with NSCLC (340.1±1011.0 ng/mL), 7 out of 34 (20.6%) patients with Ms (26.7±94.1 ng/mL), one out of 44 (2.27%) benign PE (1.5±1.2 ng/mL), and in none patients with mesotheliomas (0.97±0.83 ng/mL). In diagnosing NSCLC, pCEA was very sensitive (97%), whereas in benign PE it was extremely specific (98%), resulting in an overall diagnostic accuracy of 97% and a prevalence of 46% (NSCLS vs. benign PE). Our preliminary results suggest that pCEA is effective and highly accurate, particularly in differentiating NSCLC from benign lesions, and mesotheliomas from NSCLC. In case of suspicious MPE with negative cytological findings and no visualized cancer on CT scan or 18F-FDG-PET, pCEA measurement should be considered a simple and accurate tool, indicating the need for pleural biopsy.