PT - JOURNAL ARTICLE AU - Edwin Jabbari AU - John Woodside AU - Tong Guo AU - Nadia K Magdalinou AU - Viorica Chelban AU - Dilan Athauda AU - Andrew J Lees AU - Thomas Foltynie AU - Henry Houlden AU - Alistair Church AU - Michele TM Hu AU - James B Rowe AU - Henrik Zetterberg AU - Huw R Morris TI - Proximity extension assay testing reveals novel diagnostic biomarkers of atypical parkinsonian syndromes AID - 10.1136/jnnp-2018-320151 DP - 2019 Jul 01 TA - Journal of Neurology, Neurosurgery & Psychiatry PG - 768--773 VI - 90 IP - 7 4099 - http://jnnp.bmj.com/content/90/7/768.short 4100 - http://jnnp.bmj.com/content/90/7/768.full SO - J Neurol Neurosurg Psychiatry2019 Jul 01; 90 AB - Objective The high degree of clinical overlap between atypical parkinsonian syndromes (APS) and Parkinson’s disease (PD) makes diagnosis challenging. We aimed to identify novel diagnostic protein biomarkers of APS using multiplex proximity extension assay (PEA) testing.Methods Cerebrospinal fluid (CSF) samples from two independent cohorts, each consisting of APS and PD cases, and controls, were analysed for neurofilament light chain (NF-L) and Olink Neurology and Inflammation PEA biomarker panels. Whole-cohort comparisons of biomarker concentrations were made between APS (n=114), PD (n=37) and control (n=34) groups using logistic regression analyses that included gender, age and disease duration as covariates.Results APS versus controls analyses revealed 11 CSF markers with significantly different levels in cases and controls (p<0.002). Four of these markers also reached significance (p<0.05) in APS versus PD analyses. Disease-specific analyses revealed lower group levels of FGF-5, FGF-19 and SPOCK1 in multiple system atrophy compared with progressive supranuclear palsy and corticobasal syndrome. Receiver operating characteristic curve analyses suggested that the diagnostic accuracy of NF-L was superior to the significant PEA biomarkers in distinguishing APS, PD and controls. The biological processes regulated by the significant proteins include cell differentiation and immune cell migration. Delta and notch-like epidermal growth factor-related receptor (DNER) had the strongest effect size in APS versus controls and APS versus PD analyses. DNER is highly expressed in substantia nigra and is an activator of the NOTCH1 pathway which has been implicated in the aetiology of other neurodegenerative disorders including Alzheimer’s disease.Conclusions PEA testing has identified potential novel diagnostic biomarkers of APS.