Diagnostic utility of serum and pleural fluid carcinoembryonic antigen, neuron-specific enolase, and cytokeratin 19 fragments in patients with effusions from primary lung cancer

Study objectives: To assess the diagnostic values of carcinoembryonic antigen (CEA), neuron-specific enolase (NSE), and cytokeratin 19 fragments (CYFRA 21-1) as markers of pleurisy in primary lung cancer. Design: Prospective case-control study. Setting: A tertiary university hospital. Patients: Thirty-four patients with lung cancer and 16 patients with tuberculous pleurisy. Measurements and results: Levels of CEA, NSE, and CYFRA 21-1 were measured by immunoassay in the serum and pleural fluid of patients with lung cancer and of patients with tuberculous pleurisy. Patients with lung cancer were found to have significantly higher serum and pleural fluid levels of CEA and CYFRA 21-1 than patients with tuberculous pleurisy. Using cutoff values of 5 ng/mL, 20 ng/mL, and 3.3 ng/mL for serum CEA, NSE, and CYFRA 21-1, respectively, the sensitivities and specificities of these tumor markers were as follows for differentiating malignant effusion from benign: CEA, 68% and 93%; NSE, 34% and 93%; and CYFRA 21-1, 45% and 100%. Using cutoff values of 5 ng/mL, 20 ng/mL, and 45 ng/mL for pleural fluid, the sensitivities and specificities were as follows: CEA, 82% and 94%; NSE, 36% and 94%; and CYFRA 21-1, 61% and 81%. A combination of pleural fluid CEA and NSE increased sensitivity and specificity. Conclusions: In the diagnosis of malignant effusion associated with lung cancer, the determinations of CEA and NSE in pleural fluid could enhance diagnostic yield better than those of all three tumor markers.