**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.**
Natasha Burke, Amyloidosis Center, Boston University Chobanian & Avedisian School of Medicine and Boston Medical Center, Boston, MA.

**Main Body of the Abstract**
Background:  Congo red (CR) staining of surrogate tissues (e.g., abdominal fat pad and bone marrow [BM] core) provides a minimally invasive means to diagnosing amyloidosis. The aim of this study was to evaluate the amyloid detection rates of surrogate tissues across classes of systemic amyloidosis.
Methods:  We identified patients with systemic amyloidosis (grouped: AL, ATTRwt, non-V122I-ATTRv, ATTRV122I, AA and other amyloidosis) who were seen at the Boston University Amyloidosis Center between 1968–2023 and had at least one surrogate tissue biopsy stained with CR. Amyloid detection rates of biopsy samples were analyzed.
Results:  The cohort comprised 4,027 patients, of whom 3,873 had an abdominal fat pad aspirate and 2,598 had a BM core biopsy for CR staining. The CR positivity rates of these surrogate tissues are shown in Table 1. AL amyloidosis had the highest CR positivity rates, whereas ATTRwt amyloidosis had the lowest. Amyloid detection in BM core samples was non-specific to AL amyloidosis; 74 positive samples were among patients with non-AL amyloidosis.
In the AL amyloidosis cohort, the amyloid detection rate was 73% with fat pad aspirate only and 53% with BM biopsy only. When fat pad aspirate and BM biopsy were performed together (n=2,213), the detection rate increased to 85% (n=879, 40% in both samples; n=713, 32% in fat pad only; n=285, 13% in BM core only).
Conclusions:  The yield of surrogate tissues for detecting amyloid deposits depends on the biopsy site and class of amyloidosis. Detecting amyloid deposits in the BM is non-specific to AL 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.**
Natasha Burke, _Amyloidosis Center, Boston University Chobanian & Avedisian School of Medicine and Boston Medical Center, Boston, MA._

**Main Body of the Abstract**
**Background:**  Congo red (CR) staining of surrogate tissues (e.g., abdominal fat pad and bone marrow [BM] core) provides a minimally invasive means to diagnosing amyloidosis. The aim of this study was to evaluate the amyloid detection rates of surrogate tissues across classes of systemic amyloidosis.
**Methods:**  We identified patients with systemic amyloidosis (grouped: AL, ATTRwt, non-V122I-ATTRv, ATTRV122I, AA and other amyloidosis) who were seen at the Boston University Amyloidosis Center between 1968–2023 and had at least one surrogate tissue biopsy stained with CR. Amyloid detection rates of biopsy samples were analyzed.
**Results:**  The cohort comprised 4,027 patients, of whom 3,873 had an abdominal fat pad aspirate and 2,598 had a BM core biopsy for CR staining. The CR positivity rates of these surrogate tissues are shown in **Table 1**. AL amyloidosis had the highest CR positivity rates, whereas ATTRwt amyloidosis had the lowest. Amyloid detection in BM core samples was non-specific to AL amyloidosis; 74 positive samples were among patients with non-AL amyloidosis.
In the AL amyloidosis cohort, the amyloid detection rate was 73% with fat pad aspirate only and 53% with BM biopsy only. When fat pad aspirate and BM biopsy were performed together (n=2,213), the detection rate increased to 85% (n=879, 40% in both samples; n=713, 32% in fat pad only; n=285, 13% in BM core only).
**Conclusions:**  The yield of surrogate tissues for detecting amyloid deposits depends on the biopsy site and class of amyloidosis. Detecting amyloid deposits in the BM is non-specific to AL amyloidosis.



The Detection Yield of Surrogate Tissue Biopsies across Classes of Systemic Amyloidosis: Review of 4,027 Cases PA98 (#372)

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.