LAUSR

INTRODUCTION Systemic amyloidosis is a histological diagnosis, often achieved via critical organ biopsy. Screening biopsies represent a low-risk approach to diagnosis. OBJECTIVES AND METHODS All patients with systemic AL and ATTR amyloidosis who underwent abdominal fat aspiration (AFA) and either a bone marrow (BM) or gastrointestinal (GI) biopsy at the UK National Amyloidosis Centre (2006-2019) were identified. We sought to determine diagnostic sensitivity in relation to whole body amyloid burden, amyloid type, and organ involvement RESULTS: Diagnostic sensitivity, established in 471 patients with AL (n=321) and ATTR (n=150) amyloidosis respectively was 73.2% and 27.3% for AFA (p< 0.001), 59.7% and 42.2% for BM (p< 0.001), 74.6% and 44.6% for GI biopsy (p< 0.001). ATTR amyloid deposits were detected in 35.4% BMs and 33.3% of GI biopsies when AFA did not demonstrate amyloid. In AL amyloidosis, sensitivity of combined AFA and BM biopsy in AL amyloidosis was 82.9%. There was a strong association between whole body amyloid burden and sensitivity of each screening biopsy method. The diagnostic sensitivity of screening biopsies ranged from 80.0-90.5% for patients with a large amyloid load on 123 I-SAP scintigraphy in comparison to 53.9-79.0% in those with no visceral amyloid visible on imaging. CONCLUSION Performing both AFA and BMB should be considered in suspected AL amyloidosis to substantially reduce the clinical risk associated with critical organ biopsy. The sensitivity of screening biopsies in ATTR amyloidosis is poor.