**Author Listing - Lead/ Submitting Author (we will be communicating with this individual): Name, Institution, City and State where the work was done. Co-authors will be added in a separate section.**
Milou Berends
Department of Internal Medicine, University Medicial Center Groningen, Groningen Amyloidosis Center of Expertise
Groningen, the Netherlands

**Main Body of the Abstract**
Objective: We compared the gold standard single molecule array (Simoa) assay and Meso Scale Discovery (MSD) R-PLEX assay for measuring serum neurofilament light chain (sNfL), an early and sensitive biomarker of polyneuropathy. We aimed to identify a high performance and well accessible assay for sNfL measurement in hereditary transthyretin (ATTRv) amyloidosis.
Methods: sNfL levels were measured in serum samples collected between January 2000 and December 2021 from pathogenic transthyretin gene (TTR) variant carriers and ATTRv amyloidosis patients. In each sample, sNfL levels were assessed using both the Simoa and MSD R-PLEX assays allowing direct comparison of the assays.
Results: A total of 332 samples were evaluated in 72 subjects. sNfL levels measured with the MSD R-PLEX assay (median 128.7 pg/mL, interquartile range (IQR) 58.8–279.3) were consistently 4.9 times higher than those measured by the Simoa assay (median 26.4 pg/mL, IQR 11.3–50.2), p<0.0001. A strong correlation was found between levels measured with both assays (Pearson correlation coefficient 0.93, p<0.0001) (Figure 1). Bland-Altman analysis showed, within the 95% limit of agreement, a mean constant bias of 130.4% for sNfL concentrations determined by the MSD R-PLEX assay compared to the Simoa assay. The quantitative difference between the assays seems related to the internal reference provided with the tests. This study will be expanded with sNfL levels of healthy controls.
Conclusion: The MSD R-PLEX assay emerges as a robust and sensitive alternative to the Simoa assay for measuring sNfL in ATTRv amyloidosis.



**Author Listing - Lead/ Submitting Author (we will be communicating with this individual): Name, Institution, City and State where the work was done. Co-authors will be added in a separate section.**
Milou Berends
Department of Internal Medicine, University Medicial Center Groningen, Groningen Amyloidosis Center of Expertise
Groningen, the Netherlands

**Main Body of the Abstract**
**Objective:** We compared the gold standard single molecule array (Simoa) assay and Meso Scale Discovery (MSD) R-PLEX assay for measuring serum neurofilament light chain (sNfL), an early and sensitive biomarker of polyneuropathy. We aimed to identify a high performance and well accessible assay for sNfL measurement in hereditary transthyretin (ATTRv) amyloidosis.
**Methods:** sNfL levels were measured in serum samples collected between January 2000 and December 2021 from pathogenic transthyretin gene (_TTR_) variant carriers and ATTRv amyloidosis patients. In each sample, sNfL levels were assessed using both the Simoa and MSD R-PLEX assays allowing direct comparison of the assays.
**Results:** A total of 332 samples were evaluated in 72 subjects. sNfL levels measured with the MSD R-PLEX assay (median 128.7 pg/mL, interquartile range (IQR) 58.8–279.3) were consistently 4.9 times higher than those measured by the Simoa assay (median 26.4 pg/mL, IQR 11.3–50.2), p<0.0001. A strong correlation was found between levels measured with both assays (Pearson correlation coefficient 0.93, p<0.0001) (Figure 1). Bland-Altman analysis showed, within the 95% limit of agreement, a mean constant bias of 130.4% for sNfL concentrations determined by the MSD R-PLEX assay compared to the Simoa assay. The quantitative difference between the assays seems related to the internal reference provided with the tests. This study will be expanded with sNfL levels of healthy controls.
**Conclusion:** The MSD R-PLEX assay emerges as a robust and sensitive alternative to the Simoa assay for measuring sNfL in ATTRv amyloidosis.



Comparison of the Simoa and MSD R-PLEX assay to assess serum neurofilament light chain levels in hereditary transthyretin amyloidosis PB30 (#225)

We invite you to attend the XIX International Symposium on Amyloidosis to be held in Rochester, MN.

This symposium is organized as a hybrid meeting (with the focus on in-person) held from Sunday, May 26 through Thursday, May 30, 2024.

Together with the ISA Board and members of Mayo Clinic, a very attractive scientific hybrid program is being planned. The program will cover a variety of types of systemic amyloidosis: ATTR (hereditary and wild-type), AL (light-chain), AA and less frequent forms. There will be key lectures, specific symposia including those company sponsored, oral presentations and poster sessions of accepted abstracts.

COURSE DESCRIPTION
This program will provide a comprehensive review of state-of-the-art education in systemic amyloidosis: basic science, pathophysiology, diagnosis, current and emerging treatments. Scientific presentations will include competitive oral and poster abstracts. The rapid evolution of scientific discovery and expanding treatment options has created tremendous interest in the field and this meeting will fill and important gap in educating scientists and clinicians.