Objective: To establish a multicenter PSP registry and biorepository in a province covering an area of 5,500,000 inhabitants, with 14 local and university hospitals.

Background: MDS PSP diagnostic criteria besides adding new phenotypes to the classical presentation, have introduced the suggestive category, aimed at identifying early disease stage cases. Large studies are needed to define early disease, but these are challenging due to PSP rareness. In this setting, multicenter registries including biomarkers are valuable.

Method: Under ethics committee approval and after signed written consent of each participant, 116 PSP cases have been recruited between April 2021 and March 2023, and their demographic and clinical data (along with blood and CSF samples, when possible) have been collected. Cross-sectional baseline results are presented.

Results: Of the 116 cases, 51% are men and 49% women. Regarding diagnostic certainty, 72% are probable, 9% possible and 19% suggestive. As for phenotypes, 46% are PSP-RS, 32% PSP-P, 6% PSP-PGF, 8% PSP-CBS, 6% PSP-SL and 3% PSP-F. Of the 51 with CSF a-syn RT-QuIC available, 38 (70%) have been negative (25 probable, 5 possible and 8 suggestive, with 12 being PSP-P) and 13 (30%) positive (9 probable and 4 suggestive, with 7 being PSP-P). The proportion of negative a-syn RT-QuIC was 77% among probable or possible cases and 66% among suggestive ones. Among positive a-syn RT-QuIC 54% had PSP -P whereas among negative cases, 32% had PSP-P. As for NFL, median ELISA CSF levels were 1503.95pg/mL (IQR=1057.82-2455.52) and median SIMOA blood levels were 18.49pg/mL (IQR=12.65-28.74), with a significant correlation between those (rho=0.65; p=0.00001) (n= 38). NFL levels did not significantly differ between diagnostic certainty categories, nor phenotypes.

Conclusion: The multicenter registry has allowed for recruiting a large sample. Probable certainty and PSP-RS phenotype are the most frequent cases. CSF and blood NFL levels significantly but modestly correlate. a-syn RT-QuIC is negative in the majority of cases, but positivity is greater than expected as per published copathology rates. False positivity, misdiagnosis (mostly of PD as PSP-P), and cross-seeding are potential explanations that deserve further research.

[Funded by Fundació La Marató de TV3: 148/U/2020]

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MDS Abstracts - https://www.mdsabstracts.org/abstract/psp-registry-preliminary-cross-sectional-results-of-the-first-2-years-of-recruitment-of-a-multicenter-registry-and-biorepository/