To date, several detection methods, including electrochemistry (EC)-, photoelectrochemistry (PEC)-, electrochemiluminescence-, surface-enhanced Raman scattering-, fluorescence-, and chemiluminescence-based immunoassays have been utilized to trace CEA detection in the early diagnosis of various cancers [8,9,10,11,12,13]. The gene discussed is CEACAM5; the disease is cancer.