Odour discrimination and identification as a biomarker of long-term disability worsening in multiple sclerosis.

BACKGROUND: Odour discrimination and identification (DI) are markers associated with disability worsening and neuroaxonal damage in multiple sclerosis (MS). OBJECTIVE: The main objective of this research is to investigate whether longitudinal change of DI predicts long-term MS disease course. METHODS: This is a 6-year prospective longitudinal study on MS patients at the MS Clinic Innsbruck. Clinical, bi-annual visits assessed patients' history and Expanded Disability Status Scale (EDSS) score. DI and cognitive function were assessed at baseline (BL), Year 1 (Y1), Year 2 (Y2) and Year 6 (Y6) by the 'Sniffin' Sticks'/Symbol Digit Modalities Test. RESULTS: Around 92 of 139 patients were available for Y6 follow-up. Mean DI scores significantly decreased over time (BL = 27.8, Y1 = 27.5, Y2 = 26.3 and Y6 = 26.3; p < 0.001) and negatively correlated with patients' age (rs = -0.120, p = 0.032) and disease duration (rs = -0.103, p = 0.041). Multivariable regression analyses revealed that lower absolute DI scores and larger DI score loss over time were associated with higher probability of EDSS worsening (per -1 point: hazard ratio (HR) = 1.40 (1.16-1.68) and 2.34 (1.27-4.21)), progression independent of relapse activity (PIRA) (HR = 1.49 (1.20-1.85) and 2.22 (1.33-3.31)) and cognitive deterioration (HR = 1.75 (1.35-2.27) and 4.29 (1.26-2.84)) at Y6, but not with time to first relapse. CONCLUSION: Odour DI is an irreversible marker of neuroaxonal damage, associated with PIRA, cognitive deterioration and EDSS worsening.

Retinal layer thinning as a biomarker of long-term disability progression in multiple sclerosis.

BACKGROUND: Peripapillary retinal nerve fibre layer and macular ganglion cell plus inner plexiform layer thinning are markers of neuroaxonal degeneration in multiple sclerosis. OBJECTIVE: We aimed to investigate the value of peripapillary retinal nerve fibre layer and ganglion cell plus inner plexiform layer thinning for prediction of long-term disability. METHODS: This is a 6-year prospective longitudinal study on 93 multiple sclerosis patients. Optical coherence tomography scans were performed at baseline, after 1, 2 and 6 years. Primary endpoint was disability progression after 6 years, defined as expanded disability status scale worsening and/or cognitive deterioration. Univariate and multivariate analysis was used to investigate the value of peripapillary retinal nerve fibre layer and ganglion cell plus inner plexiform layer to predict the primary endpoint. RESULTS: A total of 57 (61.3%) patients had disability worsening, 40 (43.0%) expanded disability status scale worsening and 34 (36.6%) cognitive deterioration. Mean peripapillary retinal nerve fibre layer and ganglion cell plus inner plexiform layer baseline thickness were 93.0 and 75.2 µm, and mean annualised peripapillary retinal nerve fibre layer and ganglion cell plus inner plexiform layer thinning rates over 6 years were 1.3 and 1.6 µm, respectively. Univariate and multivariate analysis revealed lower peripapillary retinal nerve fibre layer and ganglion cell plus inner plexiform layer baseline thickness and higher annualised thinning rates in patients with disability progression after 6 years. Effects were more pronounced for ganglion cell plus inner plexiform layer and expanded disability status scale worsening than for peripapillary retinal nerve fibre layer models and cognitive deterioration. CONCLUSION: Ganglion cell plus inner plexiform layer and peripapillary retinal nerve fibre layer measurements depict neurodegeneration and predict disability progression in multiple sclerosis.

Olfactory threshold as a biomarker of long-term relapse activity in multiple sclerosis.

BACKGROUND: Olfactory threshold (OT) is a marker of short-term inflammatory activity in multiple sclerosis (MS). OBJECTIVE: To investigate whether OT predicts long-term MS clinical disease course. METHODS: This was a 6-year prospective longitudinal study on MS patients at the MS clinic Innsbruck. Clinical visits assessing the occurrence of relapses, Expanded Disability Status Scale (EDSS) scores, and disease-modifying treatment (DMT), were conducted biannually. OT testing was performed at baseline (BL), year 1 (Y1), year 2 (Y2) and year 6 (Y6), using the threshold subscore of the "Sniffin' Sticks" test. Cognitive function was assessed by the Symbol Digit Modalities Test. RESULTS: Of 139 MS patients, 92 were eligible for Y6 follow-up. 68% experienced relapses, 53% EDSS worsening, 29% progression independent of relapse activity (PIRA) and 41% cognitive deterioration. OT scores were lower at BL, Y1 and Y2 in patients requiring DMT escalation. In multivariable analysis, higher OT scores at BL, Y1, Y2 and Y6 were associated with lower risk of relapse (hazard ratio, HR: 0.65-0.92) and EDSS worsening (HR: 0.86-0.89), while no associations were found for PIRA and cognitive deterioration. CONCLUSIONS: OT is a potential surrogate marker for long-term inflammatory disease activity and DMT failure in MS.