Detection yield of surrogate tissue biopsies across amyloidosis classes: a large-scale analysis of 4,027 patients
Natasha J Burke1, Lisa M Mendelson1, Tracy Joshi1
1Amyloidosis Center, Boston University Chobanian & Avedisian School of Medicine and Boston Medical Center, Boston, MA, USA.
Background:
Congo red (CR) staining of surrogate tissues, such as the abdominal fat pad (FP) or bone marrow (BM), provides a minimally invasive approach to diagnosing systemic amyloidosis. This study evaluated the diagnostic yield of surrogate tissue biopsies across amyloidosis classes.
Methods:
We retrospectively analyzed 4,027 patients with systemic amyloidosis (1968-2023) who underwent CR staining of FP aspirates (n = 3,873) and/or BM core biopsies (n = 2,598). Detection rates were compared by amyloidosis class and biopsy site.
Results:
AL amyloidosis had the highest CR positivity rates (FP: 73%; BM: 53%), whereas ATTRwt amyloidosis had the lowest (FP: 22%; BM: 26%). CR positivity in BM was not exclusive to AL amyloidosis; 74 CR-positive BM biopsies were in non-AL cases. Among 2,213 patients with AL amyloidosis who underwent both FP and BM sampling, combined testing increased detection to 85% (40% positive in both; 32% FP-only; 13% BM-only). Higher CR positivity grades in FP aspirates correlated with shorter survival in AL amyloidosis but not in other amyloidosis classes.
Conclusions:
The diagnostic yield of CR-stained surrogate tissue biopsies varies by amyloidosis class and biopsy site. In AL amyloidosis, combining FP and BM sampling enhances detection, and FP CR positivity grade offers prognostic insight.
