CXCL12 levels correlated most positively with NEFL in PDD (rs = 0.40; P = 0.023), and these correlations were lesser in healthy (rs = 0.12; P = 0.394) and PD-NCI (rs = 0.17; P = 0.326) subjects (ANCOVA (F (2,114) = 3.484, P = 0.031); Fig. 3C). The gene discussed is CXCL12; the disease is Parkinson disease.