Originally Posted on JAMA Neurology | 5 December 2016
IMPORTANCE Parkinson disease (PD) is a highly prevalent and incurable neurodegenerative brain disease associated with the accumulation of misfolded α-synuclein (αSyn) aggregates. An important problem in this disease is the lack of a sensitive, specific, and noninvasive biochemical diagnosis of Parkinson disease to help in clinical evaluation, monitoring of disease progression, and early differential diagnosis from related neurodegenerative diseases.
OBJECTIVE To develop a novel assay with high sensitivity and specificity to detect small quantities of αSyn aggregates circulating in cerebrospinal fluid (CSF) of patients affected by PD and related synucleinopathies.
DESIGN, SETTING, AND PARTICIPANTS The strategy evaluated in this proof-of-concept study uses the protein misfolding cyclic amplification (PMCA) technology that detects minute amounts of misfolded oligomers by taking advantage of their ability to nucleate further aggregation, enabling a very high amplification of the signal. The technology was first adapted with synthetic αSyn oligomers prepared in vitro and used to screen in 2 blinded cohorts of CSF samples from German and Japanese patients with PD (n = 76) and individuals serving as controls affected by other neurologic disorders (n = 65), neurodegenerative diseases (n = 18), and Alzheimer disease (n = 14). The kinetics of αSyn aggregation were measured by αSyn-PMCA in the presence of CSF samples from the participants to detect αSyn oligomeric seeds present in this biological fluid. The assays were conducted from November 15, 2013, to August 28, 2015.
MAIN OUTCOMES AND MEASURES Kinetic parameters correlated with disease severity at the time of sample collection, measured by the Hoehn and Yahr scale, with the lowest grade indicating unilateral involvement with minimal or no functional impairment, and the highest grade defining patients with complete confinement to wheelchair or bed.
RESULTS Studies with synthetic αSyn aggregates showed that αSyn-PMCA enabled to detect as little as 0.1 pg/mL of αSyn oligomers. The αSyn-PMCA signal was directly proportional to the amount of αSyn oligomers added to the reaction. A blinded study of CSF samples correctly identified patients affected by PD with an overall sensitivity of 88.5% (95% CI, 79.2%-94.6%) and specificity of 96.9% (95% CI, 89.3%-99.6%). The αSyn-PMCA results for different patients correlated with the severity of the clinical symptoms of PD (Japanese cohort: rs = −0.54, P= .006; German cohort: rs = −0.36, P = .02).
CONCLUSIONS AND RELEVANCE The findings suggest that detection of αSyn oligomers by αSyn-PMCA in the CSF of patients affected by PD may offer a good opportunity for a sensitive and specific biochemical diagnosis of the disease. Further studies are needed to investigate the usefulness of αSyn-PMCA to monitor disease progression and for preclinical identification of patients who may develop PD.
Question Does detection of α-synuclein oligomers by protein misfolding cyclic amplification (PMCA) in cerebrospinal fluid provide a sensitive and specific biochemical test for the diagnosis of Parkinson disease?
Findings α-Synuclein PMCA enabled detection of attomole quantities of α-synuclein oligomers and identification in cerebrospinal fluid samples from 76 patients affected by Parkinson disease and 97 individuals with other neurologic disorders with 88.5% sensitivity and 96.9% specificity. Moreover, good correlation was observed between the α-synuclein–PMCA results and the disease progression.
Meaning Our findings suggest that α-synuclein–PMCA may provide an efficient, objective and non-invasive biochemical test for the diagnosis of Parkinson disease.
Related Articles on Neurodegeneration:
- Meet the Prions: Synuclein is the Molecular Basis for Parkinson’s
- Early Detection is Key to Preventive Brain Care
- Neurodegenerative Brain Diseases & Protein Misfolding
- The Role Of Protein Misfolding in Neurodegenerative Diseases