SPP1 and Parkinson disease: In addition, the fluorescence-based Simple PlexTM Human OPN assay observed increased osteopontin levels in plasma from patients with Parkinson’s disease (p = 0.0011) or multiple sclerosis (p = 0.0071) in comparison to healthy controls as well as decreased osteopontin concentration in CSF of patients with multiple sclerosis (p = 0.0219) in comparison to healthy controls (Figure 5A,B).