After combination with CSF Aβ42, the diagnostic accuracy of CSF GAP-43 had been significantly increased, even showing no significant difference compared with the combination of P-tau and Aβ42 for MCI ε4+ (GAP-43 and Aβ42 versus P-tau and Aβ42, p  =  0.071), AD ε4− (GAP-43 and Aβ42 versus P-tau and Aβ42, p  =  0.905), and AD ε4+ (GAP-43 and Aβ42 versus P-tau and Aβ42, p  =  0.127; Supplementary Table S1). The gene discussed is MAPT; the disease is Alzheimer disease.