Disclosure(s): No financial relationships with ineligible companies to disclose
Background/Purpose: Spectral analysis of liquid biopsies has recently emerged as a promising, non-invasive approach to improve the diagnosis of various pathologies. Our objective was to develop a rapid and precise strategy to differentiate among clinically challenging rheumatic inflammatory and autoimmune diseases, as well as to assess their severity, by analyzing the spectral properties of peripheral blood. Methods: We recruited patients with rheumatoid arthritis (RA, n=47), ankylosing spondylitis (AS, n=27), fibromyalgia syndrome (FMs, n=43), along with healthy controls (n=45). Disease activity was assessed using the Disease Activity Score-28 (DAS-28) for RA, the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) for AS, and the Fibromyalgia Impact Questionnaire (FIQ) for FMs. Plasma concentrations of inflammatory cytokines (TNF-α, IL-1β, IL-6, IL-17A and IFN-γ) were quantified via U-Plex ELISA (Meso Scale Diagnostics, USA). Peripheral blood mononuclear cells (PBMC) were isolated by standard density-gradient centrifugation (Lymphoprep™). Mid-infrared (Mid-IR) spectra were acquired from plasma and PBMC’s supernatants using a Bruker V80 Fourier-transform infrared (FTIR) spectrometer. Correlation coefficient analysis was performed to relate specific spectral features to clinical scores and cytokine levels. Results: Spectral analysis of plasma samples generated distinct spectral “fingerprints” that reliably distinguished FMs patients from those with RA, AS and healthy controls (Fig. 1). Notably, several infrared spectral features showed strong correlations with RA disease activity (e.g., DAS28) (Fig.2) and inflammatory cytokine levels (e.g. IL-6, IL-17A), indicating that spectral markers reflect underlying inflammatory burden. Furthermore, spectral analysis of PBMC-derived supernatants from rheumatic patients, following activation (LPS/PHA) and treatment with anti-inflammatory drugs, corelated with biological data reflecting the inflammatory status of the cells (Fig. 3). Conclusion: Integrating Mid-IR spectral profiling of liquid biopsies (such as patients-derived plasma or -immune cells’ supernatants) with established clinical and biological parameters provides a powerful, non-invasive modality for differential diagnosis and severity stratification of rheumatic diseases. This approach has the potential to improve diagnostic accuracy and guide personalized treatment strategies in rheumatology.
