Besides, the consistency of the present results about Ng and AD is acceptable, but the other findings need more interpretation, such as the association of Ng with PD (Selnes et al., 2017; Hall et al., 2020), neuro-HIV (Guha et al., 2018; Yilmaz et al., 2019), FTD (Byrne et al., 2018; Clarke et al., 2019), etc., which in part attributes to the current measuring methods lacking high accuracy in detecting the proteins of extremely low levels both in CSF and blood. This evidence concerns the gene NRGN and Parkinson disease.