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

Klaus Berek; Harald Hegen; Michael Auer; Robert Barket; Franziska Di Pauli; Jakob Hocher; Nik Krajnc; Anne Zinganell; Florian Deisenhammer; Thomas Berger; Gabriel Bsteh

doi:10.1016/j.msard.2024.105545

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

Mult Scler Relat Disord. 2024 Mar 11:85:105545. doi: 10.1016/j.msard.2024.105545. Online ahead of print.

Authors

Affiliations

¹ Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
² Department of Neurology, Medical University of Vienna, Waehringer Guertel 18-20, Vienna 1090, Austria; Comprehensive Center for Clinical Neurosciences and Mental Health, Medical University of Vienna, Vienna, Austria.
³ Department of Neurology, Medical University of Vienna, Waehringer Guertel 18-20, Vienna 1090, Austria; Comprehensive Center for Clinical Neurosciences and Mental Health, Medical University of Vienna, Vienna, Austria. Electronic address: gabriel.bsteh@meduniwien.ac.at.

PMID: 38479044
DOI: 10.1016/j.msard.2024.105545

Abstract

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.

Keywords: Biomarker; Disease activity; Multiple sclerosis; Olfactory function; Relapse.