Neurodegenerative and inflammatory biomarkers are detectable in saliva in multiple sclerosis

The growing incidence of multiple sclerosis (MS), a neuroinflammatory and neurodegenerative disease, poses challenges for healthcare, as diagnosis and monitoring rely on expensive and/or invasive procedures, including MRI and lumbar puncture. Biomarkers in more accessible biofluids than CSF (serum, saliva, nasal secretion, tears) may aid early diagnosis and monitoring of progression and response to treatment. We investigated MS-associated biomarkers in accessible biofluids collected from 37 people living with MS and 23 healthy controls. Biomarkers analysed were neurofilament light chain (NfL), glial fibrillary acidic protein (GFAP), free light chains (κFLC and λFLC), chitinase-3-like 1 (CH3L1), chemokine-ligand-13 (CXCL13) and soluble triggering receptor expressed on myeloid cells (sTREM2). Linear regression analyses were used to determine mean differences between experimental groups and diagnostic accuracy of biomarkers assessed by generating receiver operating characteristic (ROC) curves. All biomarkers were measurable in both serum and saliva. All but CXCL13 and sTREM2 were detectable in nasal secretion samples, but none were detectable in tears. Levels of NfL (p = 0.03), κFLC (p = 0.003), and CHI3L1 (p = 0.021) were all significantly higher in the saliva samples of people with MS. Our findings suggest that these biomarkers are detectable in the proposed sample types, and, particularly in saliva, show potential in identifying inflammation and neurodegeneration in MS. Follow-up longitudinal studies with a larger cohort are needed to establish these methods as inexpensive and non-invasive means of monitoring MS.