KRT19 and lung adenocarcinoma: For example, LG3BP and C163A demonstrate low specificity for larger nodules,[33] the sensitivity of cfDNA in plasma is influenced by multiple factors and the specificity remains inadequate.[34] Compared to widely employed biomarkers such as carcinoembryonic antigen (CEA) and cytokeratin 19 fragment (CYFRA 21–1), a study involving a cohort of 300 serum samples demonstrated that serum CEA levels for diagnosing lung adenocarcinoma (LUAD) yielded an area under the curve (AUC) of 0.67, with a sensitivity of 24.6% at a specificity of 97.6%.