Enhanced quantitative method for the diagnosis of grade 1 cardiac amyloidosis in 99 mTc-DPD scintigraphy

• Published in: Scientific reports Vol. 12; no. 1; p. 1740
• Main Authors: Mallón Araujo, María Del Carmen, Abou Jokh Casas, Estephany, Abou Jokh Casas, Charigan, Aguiar Fernández, Pablo, Martínez Monzonís, María Amparo, Sopeña Pérez-Argüelles, Bernardo, Pubul Núñez, Virginia
• Format: Journal Article
• Language: English
• Published: England 02.02.2022
• Subjects: Amyloid Neuropathies, Familial - diagnostic imaging; Amyloid Neuropathies, Familial - pathology; Amyloidosis - diagnostic imaging; Amyloidosis - pathology; Humans; Immunoglobulin Light Chains - metabolism; Myocardium - pathology; Organotechnetium Compounds; Radionuclide Imaging - methods; Radiopharmaceuticals; Retrospective Studies; Severity of Illness Index; Sulfur Compounds
• ISSN: 2045-2322

The lack of a standardized cut-off value in the quantitative method and an inter-observer disagreement in the evaluation of the semiquantitative score in mTc-DPD scintigraphy leaves several patients with cardiac amyloidosis (CA) undiagnosed (grade 1 and H/CL: 1-1.49). This study aims to increase diagnostic productivity of mTc-DPD scintigraphy in CA. This is a retrospective study of 170 patients with suspicion of CA. A total of 81 (47.6%) were classified as transthyretin CA (TTR-CA) and 9 (5.3%) as light-chain CA (LC-CA) applying the visual score. An enhanced quantitative method and cut-off point were attempted to reclassify inconclusive patients and reduce inter-observer variability. Applying the proposed quantitative method, of the 19 patients with grade 1 uptake, 2 became grade 0 (none-CA), 2 were reclassified as grade 3 (TTR-CA), and 2 were regrouped as grade 2 (1 TTR-CA and 1 LC-CA). Adjusting the quantitative method's cut-off value to 1.3, four patients previously inconclusive were reclassified as TTR-CA, the diagnosis was confirmed in 3 and rejected in 1. When a 1.3 threshold is compared to 1.5, the sensitivity increases to 94% without reducing its specificity. The quantitative method improves the visual interpretation, reclassifying doubtful cases. The optimization of the cut-off value from 1.5 to 1.3 reclassifies a higher percentage of patients as TTR-CA with a higher sensitivity without reducing its specificity.