The optimal cut-off values for predicting the diagnosis of primary lung adenocarcinoma were 3280 ng∙mL−1 for ELF-napsin A, with a sensitivity and specificity of 79.3% and 82.9%, respectively, and 82 ng∙mL−1 for ELF-CEA, with sensitivity and specificity values of 75.9% and 34.1%, respectively (Table 2). The gene discussed is CEACAM5; the disease is lung adenocarcinoma.