Compared with the existing clinical biomarkers such as neuron-specific enolase (NSE), carcinoembryonic antigen (CEA), and CYFRA21-1, the method showed the highest diagnostic efficiency in lung cancer (area under the curve, 0.859; 95%CI: 0.779-0.939) and stage I lung cancer (area under the curve, 0.912; 95%CI: 0.829-0.994). The gene discussed is CEACAM5; the disease is lung cancer.