When CEA > 5n/ml of pleural effusion was taken as the diagnostic threshold, the sensitivity, specificity, accuracy, positive predictive value, negative predictive value, and Youden’s index of CEA in diagnosing MPE was 74.3%, 97.0%, 85.3%, 96.3%, 78.0% and 0.71 respectively. This evidence concerns the gene CEACAM5 and Pleural effusion.