Biochemical detection of pediatric eosinophilic esophagitis using high wavenumber Raman endoscopy and stimulated Raman microscopy.

Eosinophilic esophagitis (EoE) is an immunoinflammatory condition of the esophagus characterized by an intense eosinophilic inflammation. Given its chronic and progressive course, EoE can lead to esophageal remodeling and dysphagia. Current diagnostic methods require repeated endoscopy to rate the severity of esophageal involvement and several biopsies of the esophageal mucosa for histopathologic confirmation of EoE, which can result in misdiagnosis and diagnostic delays. Raman spectroscopy (RS) is an inelastic scattering technique capable of real-time in vivo disease detection. The high wavenumber Raman spectrum contains quantitative information about the biochemical and water content in tissue. Using a pediatric endoscope-compatible fiber-optic RS probe, we acquired in vivo high wavenumber Raman spectra from 44 children with (cases) and without EoE (controls). Spectral unmixing revealed that children with active EoE had significantly altered carbohydrate, nucleic acid, collagen, non-collagen protein, lipid, and water signals allowing for differentiation from non-EoE controls and children with inactive EoE (treatment responders). These findings were verified by ex vivo analysis of esophageal biopsies with stimulated Raman scattering (SRS) microscopy, Raman microspectroscopy, and histochemical staining, which revealed significant decreases in epithelial carbohydrate content and increases in nucleic acid content in active EoE. Ex vivo SRS and RS measurements of full-thickness esophageal tissue revealed that subepithelial layers were the source of lipid and protein alterations observed in vivo. This study underscores the potential of high wavenumber RS for real-time in vivo detection of EoE and its activity status while offering comprehensive insights into the disease-specific esophageal biochemical changes validated through complementary techniques.