Abstract
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 99mTc-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 99mTc-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.
Highlights
Abbreviations CA Cardiac amyloidosis light chain (LC) Light chain TTR Transthyretin light-chain CA (LC-CA) Light-chain cardiac amyloidosis transthyretin CA (TTR-CA) Transthyretin cardiac amyloidosis H/CL Heart–contralateral hemithorax ratio
This pathology is at the center of attention, because of the advances in molecular imaging for its early diagnosis and because of the recent approval of new therapeutic strategies aimed at transthyretin stabilizers in TTR-CA and chemotherapy in LC-CA
This study aims to increase the diagnostic productivity of 99mTc-DPD scintigraphy in CA, focusing on reclassification patterns, mainly those included in the category of inconclusive or equivocal, through the development and validation of an additional cut-off point value in the 3 h post-administration of 99mTc-DPD, complementing the Perugini visual score to provide more diagnostic certainty when interpreting cardiac scintigraphy and improve existing quantification methods
Summary
Abbreviations CA Cardiac amyloidosis LC Light chain TTR Transthyretin LC-CA Light-chain cardiac amyloidosis TTR-CA Transthyretin cardiac amyloidosis H/CL Heart–contralateral hemithorax ratio. The term amyloidosis involves a heterogeneous group of subtypes (hereditary or acquired, localized or systemic)[2], characterized by extracellular deposits of insoluble abnormal fibrils, which receive the pathophysiological name of amyloid d eposits[3]. Until recently there was no specific treatment for this disease, mainly due to the need for histological tests such as an endomyocardial biopsy for its diagnosis and immunohistochemical examinations of the amyloid type. This pathology is at the center of attention, because of the advances in molecular imaging for its early diagnosis and because of the recent approval of new therapeutic strategies aimed at transthyretin stabilizers in TTR-CA and chemotherapy in LC-CA. The correct identification of the amyloid involved is vital to avoid toxic and inappropriate treatments[4]
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