Objectives There is a critical need to develop robust biomarkers for Parkinson's diasease (PD) research. We aimed to determine whether a serum biomarker could be used: to predict cognitive decline in PD or a diagnosis of PD. Five of the most promising serum biomarkers were identified based on recent and current evidence: Vitamin D, Apolipoprotein A1 (ApoA1), Uric Acid, C-reactive protein and Epidermal Growth Factor.

Method A peripheral blood sample was taken at baseline, spun in a centrifuge and then stored at −80°C. PD patients (n=641) diagnosed within 3.5 years, a control population (n=146) and patients with REM sleep behaviour disorder (n=74) were included at baseline. 3 year follow up data was available from 229 PD patients. Serum analysis was conducted either using Abbott systems or ELISA techniques. Age, gender, disease duration and seasonality (for vitamin D) were adjusted for using statistical models. Results: There was no strong evidence that the potential biomarkers predicted either baseline or change in cognition. Uric acid was lower in the PD group compared to controls (p=0.008), though this effect was not replicated in the RBD group. EGF (p<0.001) and ApoA1 (p=0.04) were both lower in RBD cases compared to controls, and Vitamin D levels were higher (p=0.009). These results should be viewed with caution however as they were not replicated in the PD group so may relate to type I errors and require further replication.Conclusion: None of the biomarkers predicted cognitive decline in the PD group. This may be because there is not yet enough follow up data to detect a signal, but they do not predict baseline cognition. EGF, Vitamin D and ApoA1 show some differences in the RBD group compared to controls, while Uric Acid was lower in the PD group. Individually, the candidate biomarkers did not predict cognitive decline or patient group. Additional data will be available by the time of the conference as data collection is.