biostudies-literatureMilani PTelethonFondazione IRCCS Policlinico San MatteoUniversity of Pavia751-759https://www.ebi.ac.uk/biostudies/studies/S-EPMC12790041biostudies-literatureUnknown7(6)<h4>Background</h4>Detection of monoclonal components (MCs) using serum and urine immunofixation (IFE) and free light chain measurement is a critical early step in diagnosing cardiac amyloidosis. Patients with MCs are referred for biopsy-based diagnostic work-up. New reference ranges for the free light chain ratio (FLCR), adjusted for age and estimated glomerular filtration rate, have been proposed.<h4>Objectives</h4>The aim of this study was to compare the diagnostic performance of the new vs the conventional FLCR in patients with light chain (AL) amyloidosis and wild-type transthyretin (ATTRwt) amyloidosis.<h4>Methods</h4>The analysis included 1,705 patients with AL amyloidosis and 675 with ATTRwt amyloidosis.<h4>Results</h4>In the AL cohort, 44 patients (3%) had negative results on seruJACC. CardioOncologyDiagnostic Performance of the New Free Light Chain Ratio in Systemic Amyloidosis.PMC12790041GJC23044Merlini GMilani PFoli ANanci MSanna GDNuvolone MBellofiore CGuida GCaminito SAlbertini RSalinaro FPerlini SBasset MFogliani ABarassi APalladini GMussinelli RBenigna FBosoni TCiardo MSadrzadeh MMazzini GGhazi Esfahani MfalseDiagnostic Performance of the New Free Light Chain Ratio in Systemic Amyloidosis.<h4>Background</h4>Detection of monoclonal components (MCs) using serum and urine immunofixation (IFE) and free light chain measurement is a critical early step in diagnosing cardiac amyloidosis. Patients with MCs are referred for biopsy-based diagnostic work-up. New reference ranges for the free light chain ratio (FLCR), adjusted for age and estimated glomerular filtration rate, have been proposed.<h4>Objectives</h4>The aim of this study was to compare the diagnostic performance of the new vs the conventional FLCR in patients with light chain (AL) amyloidosis and wild-type transthyretin (ATTRwt) amyloidosis.<h4>Methods</h4>The analysis included 1,705 patients with AL amyloidosis and 675 with ATTRwt amyloidosis.<h4>Results</h4>In the AL cohort, 44 patients (3%) had negative results on seru2025-01-01T00:00:00Z2025 Oct2026-07-15T13:28:38.048Z2026-07-05T03:08:34.432ZS-EPMC127900414093823910.1016/j.jaccao.2025.07.012