Serum miRNA-155 and TREM2 as Non-Invasive Biomarkers for Monitoring Neuroinflammation and Disease Activity in Multiple Sclerosis.

Serum miRNA-155 and TREM2 levels were investigated as potential non-invasive indicators. In this case-control study, serum miRNA-155 and TREM2 levels were evaluated in 80 patients with multiple sclerosis (MS) and 80 age- and sex-matched healthy controls. Levels were measured using qPCR and ELISA, with correlations assessed against Expanded Disability Status Scale (EDSS) scores, MRI lesion burden, and cerebrospinal fluid (CSF) markers (oligoclonal bands and immunoglobulin G index). Participants were followed for 24 months to evaluate biomarker dynamics during relapses and treatment. Patients with MS showed significantly elevated miRNA-155 and TREM2 levels compared to controls. Compared to healthy controls, the combined panel demonstrated good discriminatory performance (AUC = 0.924), with 89.0% sensitivity and 87.5% specificity. However, these metrics represent differentiation from health rather than disease specificity, as the study lacked disease control groups with inflammatory or non-inflammatory neurological disorders-a critical limitation for assessing actual diagnostic utility, performing better than the individual markers. Both biomarkers correlated moderately with EDSS (miRNA-155 r = 0.62, 95% CI 0.49-0.73; TREM2 r = 0.59, 95% CI 0.45-0.71), MRI abnormalities, and CSF parameters (r = 0.48-0.60, p < 0.001). Longitudinally, elevations tracked relapse activity, while therapy responders showed reductions (miRNA-155: -18.7%; TREM2: -15.3%), underscoring utility in monitoring treatment efficacy. These results indicate that serum miRNA-155 and TREM2 effectively capture MS neuroinflammation, structural damage, and therapeutic responses. This dual-biomarker approach provides clinicians with a practical, noninvasive tool for tracking disease progression and optimizing the management of MS.