CXCL12 and Parkinson disease: Significance persisted after validation, the logistic analysis showed that higher levels of CXCL12, CX3CL1, IL-8 and CCL15 were associated with the diagnosis of PD (OR = 2.3 for CXCL12, 2.8 for CX3CL1, 57.0 for IL-8 and 0.5 for CCL15).