Objective: Present the validation of the new proposed novel staging system (NSS) for Lewy body disease and compare it against the previously proposed staging systems.

Background: Several staging criteria have been previously proposed for the neuropathological classification of cases with deposition of α-synuclein in the form of Lewy related pathology (LRP). The previously developed neuropathological staging criteria, like the 2005 Newcastle-McKeith Dementia with Lew bodies (DLB) criteria and the 2003 Braak LRP staging system, led to a large number of cases not being classified when applied to a varied sample of neuropathological cases with LRP and to some cases fitting more than one category in some instances.

Method: We uploaded scanned slide images for 34 cases to an online server. Nine regions were included and a panel of 18 international experts semi-quantitatively rated each of the slides and classified each case based on the Newcastle-McKeith DLB 2005 third report criteria, the Braak 2003 criteria, the Leverenz 2008 criteria, the Unified Staging System criteria and the new proposed NSS to these cases. Multiple inter-rater agreement was estimated Cronbach α and confidence intervals were bootstrapped. In addition, we retrospectively applied the criteria to a sample of 204 cases with LRP to evaluate the percentage of cases not classified by each of the systems in a large representative sample of cases from a clinical brain bank.

Results: Inter-rater agreement for semi-quantitative scores for each of the evaluated areas mostly fell between the 0.70 and 0.80 range. Median percentage of unclassified cases in the prospective sample was 0% for the NSS, whereas for the other staging systems it ranged between 3-26%. In the retrospective analysis all cases were also classified by the NSS, whereas for the other staging systems up to 58.3% of the cases were not classified. The NSS also achieved one of the highest inter-rater agreements for the classification into the different staging systems.

Conclusion: The new criteria classified showed overall the best combination of classification of cases and inter-rater agreement of all the available LRP classification systems. They are also based on a dichotomous evaluation of the pathology, which simplifies the rating procedure. All these characteristics make the proposed system an easy implementable and reliable system to evaluate LRP in future studies.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/new-neuropathological-staging-system-for-lewy-body-disease/