Heterogenous relapse and efficacy endpoint definitions for neuromyelitis optica spectrum disorder studies: A systematic review.

Background: Over the last years, multiple studies have been dedicated to evaluate the efficacy of different treatment options for Neuromyelitis Optica Spectrum Disorder (NMOSD). However, there is a wide variety of endpoints employed across these studies. Our goal is to conduct a systematic review describing the endpoints utilized in studies related to NMOSD.

Methods: Medline, Embase, and Cochrane were searched from inception to May 2023, to identify studies analyzing treatment options in patients with NMOSD. We collected data on baseline study characteristics and all efficacy outcomes available.

Results: We included 127 studies and identified approximately 40 different efficacy endpoints, categorized into 1) relapse, 2) disability, 3) visual acuity, and 4) surrogate outcomes. Most studies were retrospective (54.3 %) and aimed at attack prevention (81.4 %). The most common relapse-related outcomes were annualized relapse rate (73.2 %), followed by relapse rate (50.4 %), and relapse-free rate (36.2 %). The relapse definition also varied widely among studies, with only 73 (57.4 %) studies explicitly addressing the definition used. The most common disability outcome was the Expanded Disability Scale (97.6 %), followed by the Modified Rankin Scale (7.9 %). Visual Acuity Score was employed in 14.2 % of studies, followed by Visual Evoked Potentials (6.3 %). Imaging was the most common surrogate (20.5 %), followed by the fraction of B cells (18.1 %).

Conclusion: Publications were heterogeneous in measuring efficacy, with different use of endpoints and relapse definitions. Standardization across studies would improve data analysis and application in clinical practice.