Proof-of-concept for the application of Raman spectroscopy in differentiating the subtypes of cardiac amyloidosis
Tomoya Sagawa1, Noriyuki Tanaka2, Aya Miyagawa-Hayashino3
1Inflammation and Immunology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan; Graduate School of Global Environmental Studies, Kyoto University, Kyoto, Japan.
Insights
Raman spectroscopy rapidly differentiates cardiac amyloidosis subtypes (AL and ATTR) using spectral analysis. This technique shows promise for timely diagnosis and personalized treatment of this severe heart condition.
Area of Science:
- Biomedical Spectroscopy
- Cardiovascular Pathology
- Diagnostic Technologies
Background:
- Cardiac amyloidosis is a severe condition with three main subtypes: immunoglobulin light-chain (ALκ and ALλ) and transthyretin (ATTR) amyloidosis.
- Prompt, subtype-specific treatment is crucial for improving patient outcomes, necessitating rapid diagnostic differentiation.
- Current diagnostic methods may not always provide the speed required for timely therapeutic decisions.
Purpose of the Study:
- To evaluate the utility of Raman spectroscopy for rapid, label-free differentiation of cardiac amyloidosis subtypes.
- To identify spectral features that distinguish between AL (κ and λ) and ATTR cardiac amyloidosis.
- To develop a spectroscopic model for accurate classification of cardiac amyloidosis subtypes.
Main Methods:
- Raman spectroscopy was employed on cardiac tissue sections from autopsy cases of AL and ATTR amyloidosis.
- Spectral analysis focused on the Amide I band, specifically the high-wavenumber component indicative of β-sheet structures.
- Principal component analysis (PCA) and multinomial logistic regression were used to build a classification model.
Main Results:
- An increase in β-sheet structures was observed across all cardiac amyloidosis subtypes.
- PCA identified five key loading spectra that effectively distinguished between disease subtypes.
- The developed logistic regression model achieved 94% accuracy in the training set and 85% in the validation set for subtype differentiation.
Conclusions:
- Raman spectroscopy offers a rapid, non-destructive method for differentiating cardiac amyloidosis subtypes.
- The study demonstrates proof-of-concept for using spectral data and chemometrics for diagnosis.
- Further validation with larger sample sizes is needed, but the technique holds potential for clinical application, including early detection in conditions like carpal tunnel syndrome.
Abstract:
Cardiac amyloidosis is a clinically severe condition classified into three major subtypes based on the precursor protein: immunoglobulin light-chain (κ) (ALκ) amyloidosis, immunoglobulin light-chain (λ) (ALλ) amyloidosis, and transthyretin (ATTR) amyloidosis. To improve patient outcomes, subtype-specific treatment must be initiated promptly. Therefore, rapid differentiation is required. In this study, we aimed to differentiate cardiac amyloidosis subtypes using Raman spectroscopy, which enables rapid, non-destructive, label-free and preparation-free sample analysis. Raman spectra were acquired from amyloid-deposited areas in cardiac tissue sections obtained from autopsy cases of each disease subtype and compared with spectra from non-deposited areas. An increase in the high-wavenumber component of the Amide I band, assigned to β-sheet structures, was observed across all subtypes. Focusing on this band, principal component analysis was performed, resulting in the identification of five loading spectra useful for distinguishing between disease subtypes. A multinomial logistic regression model, utilizing the principal component scores derived from these loading spectra, achieved an overall accuracy of approximately 94% for differentiating disease subtypes in the training dataset, and 85% in the validation dataset based on spectra acquired from different areas within the same samples. This proof-of-concept study is limited by the small sample size, and the findings should be validated in studies with a larger sample size. Nevertheless, given the rapidity of Raman spectroscopy, our results may have practical future utility, such as enabling rapid differentiation of disease subtypes using surgical specimens from patients with carpal tunnel syndrome, which often precedes the onset of cardiac amyloidosis.
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