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Assessment of heterogeneity among participants in the Parkinson's Progression Markers Initiative cohort using a-synuclein seed amplification: a cross-sectional study
Journal article   Open access   Peer reviewed

Assessment of heterogeneity among participants in the Parkinson's Progression Markers Initiative cohort using a-synuclein seed amplification: a cross-sectional study

Andrew Siderowf, Luis Concha-Marambio, David-Erick Lafontant, Carly M. Farris, Yihua Ma, Paula A. Urenia, Hieu Nguyen, Roy N. Alcalay, Lana M. Chahine, Tatiana Foroud, …
Lancet neurology, Vol.22(5), pp.407-417
05/01/2023
DOI: 10.1016/S1474-4422(23)00109-6
PMCID: PMC10627170
PMID: 37059509

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Abstract

Background Emerging evidence shows that alpha-synuclein seed amplification assays (SAAs) have the potential to differentiate people with Parkinson's disease from healthy controls. We used the well characterised, multicentre Parkinson's Progression Markers Initiative (PPMI) cohort to further assess the diagnostic performance of the alpha-synuclein SAA and to examine whether the assay identifies heterogeneity among patients and enables the early identification of at-risk groups. Methods This cross-sectional analysis is based on assessments done at enrolment for PPMI participants (including people with sporadic Parkinson's disease from LRRK2 and GBA variants, healthy controls, prodromal individuals with either rapid eye movement sleep behaviour disorder (RBD) or hyposmia, and non-manifesting carriers of LRRK2 and GBA variants) from 33 participating academic neurology outpatient practices worldwide (in Austria, Canada, France, Germany, Greece, Israel, Italy, the Netherlands, Norway, Spain, the UK, and the USA). alpha-synuclein SAA analysis of CSF was performed using previously described methods. We assessed the sensitivity and specificity of the alpha-synuclein SAA in participants with Parkinson's disease and healthy controls, including subgroups based on genetic and clinical features. We established the frequency of positive alpha-synuclein SAA results in prodromal participants (RBD and hyposmia) and non-manifesting carriers of genetic variants associated with Parkinson's disease, and compared alpha-synuclein SAA to clinical measures and other biomarkers. We used odds ratio estimates with 95% CIs to measure the association between alpha-synuclein SAA status and categorical measures, and two-sample 95% CIs from the resampling method to assess differences in medians between alpha-synuclein SAA positive and negative participants for continuous measures. A linear regression model was used to control for potential confounders such as age and sex. Findings This analysis included 1123 participants who were enrolled between July 7, 2010, and July 4, 2019. Of these, 545 had Parkinson's disease, 163 were healthy controls, 54 were participants with scans without evidence of dopaminergic deficit, 51 were prodromal participants, and 310 were non-manifesting carriers. Sensitivity for Parkinson's disease was 87.7% (95% CI 84.9-90.5), and specificity for healthy controls was 96.3% (93.4-99.2). The sensitivity of the alpha-synuclein SAA in sporadic Parkinson's disease with the typical olfactory deficit was 98.6% (96.4-99.4). The proportion of positive alpha-synuclein SAA was lower than this figure in subgroups including LRRK2 Parkinson's disease (67.5% [59.2-75.8]) and participants with sporadic Parkinson's disease without olfactory deficit (78.3% [69.8-86.7]). Participants with LRRK2 variant and normal olfaction had an even lower alpha-synuclein SAA positivity rate (34.7% [21.4-48.0]). Among prodromal and at-risk groups, 44 (86%) of 51 of participants with RBD or hyposmia had positive alpha-synuclein SAA (16 of 18 with hyposmia, and 28 of 33 with RBD). 25 (8%) of 310 non-manifesting carriers (14 of 159 [9%] LRRK2 and 11 of 151 [7%] GBA) were positive. Interpretation This study represents the largest analysis so far of the alpha-synuclein SAA for the biochemical diagnosis of Parkinson's disease. Our results show that the assay classifies people with Parkinson's disease with high sensitivity and specificity, provides information about molecular heterogeneity, and detects prodromal individuals before diagnosis. These findings suggest a crucial role for the alpha-synuclein SAA in therapeutic development, both to identify pathologically defined subgroups of people with Parkinson's disease and to establish biomarker-defined at-risk cohorts. Copyright (c) 2023 Elsevier Ltd. All rights reserved.
 Clinical Neurology Life Sciences & Biomedicine Neurosciences & Neurology Science & Technology

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