BackgroundMultiple sclerosis (MS) significantly affects individuals' health-related quality of life (HRQoL). Ideally, HRQoL assessment tools for MS should be patient-centered, ensuring that each item meaningfully contributes to measurement precision. The present study has three main objectives: (1) a review of the literature to identify key HRQoL domains by examining existing instruments; (2) confirmation and integration of HRQoL domains based on stakeholders' input; (3) systematic comparison of the categories and subcategories identified by the stakeholders with the domains identified in the literature review.MethodsFindings from the literature review were discussed in four focus group meetings (FGMs) with key stakeholders, including people with MS (PwMS) and healthcare professionals (HPs). Participants were purposively sampled to ensure diversity in geographic location, gender, education, and (for PwMS) disease severity. FGMs were audio-recorded, transcribed verbatim, and analyzed using qualitative content analysis by two independent researchers. The categories and subcategories generated from the qualitative analysis were then systematically compared with the items of the MS-specific HRQoL instruments identified in the literature review, by two independent researchers.ResultsOut of 5190 references, 308 records related to 9 instruments were included in the literature review. The main HRQoL domains were then extracted and discussed with the steering committee, and informed the FGM grids. The results validated the HRQoL domains identified in literature and provided deeper insights into their complexity.ConclusionThis study confirmed and added granularity to the existing HRQoL domains relevant to PwMS, identifying key areas for inclusion in future research. The findings contribute to the development of a more comprehensive, patient-centered HRQoL assessment tool, which could inform targeted interventions to enhance quality of life in PwMS.

BACKGROUND AND OBJECTIVES:Previous studies have reported inconsistent findings regarding the impact of age at onset on relapse risk in aquaporin-4 antibody-positive neuromyelitis optica spectrum disorder (AQP4-IgG NMOSD), although older disease onset has been linked to more rapid disability accrual. This is in contrast to multiple sclerosis, where advancing age and older onset are associated with reduced relapse activity, allowing for treatment de-escalation or discontinuation in some older patients. The aim of this study was to clarify the influence of age at onset on relapse risk as well as disability accrual in a large, international cohort of patients with NMOSD. METHODS:We conducted a retrospective, multicenter cohort study using the MSBase data registry to evaluate annualized relapse rates (ARRs), time to first relapse, and time to Expanded Disability Status Scale (EDSS) scores of 4 and 6. For inclusion, a diagnosis of AQP4-IgG NMOSD according to the latest iteration of the criteria and availability of the minimum data set were required. Patients were stratified as pediatric onset (<18 years of age), early onset (18-55 years inclusive) or late onset (>55 years of age). Analyses included patients on high-efficacy therapy (HET), those on low-efficacy therapy (LET), and an incident cohort with the first clinical visit within 12 months from disease onset. Predictors of first relapse and EDSS 4/6 thresholds were analyzed using Cox proportional models. RESULTS:Data from 539 patients (42 pediatric, 421 with early onset, 76 with late onset; 85.2% female) with a median age at onset of 35 years (Q1 25.10, Q3 47.60) and a disease duration of 7.42 years (Q1 3.23, Q3 13.10) were analyzed. ARR and time to first relapse were not influenced by age at disease onset. Patients on HET had fewer relapses than those on LET (p < 0.001). Older age was linked to faster disability accumulation. In addition, higher baseline EDSS scores and delayed treatment were independent predictors of future disability. DISCUSSION:Our study demonstrates that while age at onset does not affect relapse risk, older patients experience more rapid disability accrual. These findings underscore the importance of early initiation of effective preventive immunotherapy in all age groups. The primary limitations of this study pertain to its retrospective design and the sole reliance on EDSS for disability assessment.

Cognitive impairment is a common issue for people with multiple sclerosis (MS), affecting their daily lives and work. This study aimed to report the cognition and employment status of participants with highly active relapsing MS (RMS) treated with cladribine tablets (CladT) during the 2-year, open-label, single-arm, Phase 4 CLARIFY-MS study. In this post hoc analyses, 482 participants with highly active RMS received at least one dose of CladT. Cognitive function was assessed using the Brief International Cognitive Assessment for MS (BICAMS) at the start of the study (baseline [BL]), and at 12 and 24 months (M) after initiating treatment with CladT (n = 399). Symbol Digit Modalities Test (SDMT) scores were further analysed to check for clinically meaningful changes (4- and 8-point) from BL to M24. Employment status was also evaluated. Cognitive function: BICAMS parameter scores remained stable over 24 months. Most participants showed stable or improved cognitive processing speed, as measured by clinically meaningful 4- and 8-point changes in the SDMT scores from BL to M24. Employment status: No major differences in the employment status of participants were observed over 2 years, with > 40

BACKGROUND:Early initiation of high-efficacy therapies (HETs) has been associated with improved disease control in pediatric-onset multiple sclerosis (POMS). However, some children remain clinically stable on low-/moderate-efficacy therapies (METs), highlighting the need for decision-support tools. OBJECTIVE:To develop a Therapeutic Escalation Score (TES) to identify children at low risk of early escalation after initiating MET. METHODS:We analyzed treatment-naïve children with POMS who initiated MET between 2010 and 2024 in the French MS registry (Observatoire Français de la Sclérose en Plaques (OFSEP)). TES was derived using Cox regression modeling based on baseline clinical and magnetic resonance imaging (MRI) variables, with internal validation in OFSEP and external validation in the Italian MS registry Registro Italiano Sclerosi Multipla (RISM). RESULTS:We included 455 children from OFSEP (training n = 303; validation n = 152) and 573 from RISM. TES incorporated age, year of treatment initiation, Expanded Disability Status Scale score, prior-year relapses, brain lesion location, and T2 spinal cord lesions. A TES threshold of 1.34 stratified patients by 1-year escalation risk. In OFSEP, low-risk patients had a 1-year escalation probability of 3.6% (negative predictive value: 97.0%). In RISM, discrimination was similar (area under the curve (AUC): 72.8%-73.8%). CONCLUSION:TES is a baseline-only prognostic tool using routine clinical and MRI data to identify children with POMS unlikely to require early escalation after MET initiation.

BackgroundCladribine tablets are an oral short-course disease-modifying therapy (DMT) approved for the treatment of highly active relapsing multiple sclerosis (MS). While their efficacy has been demonstrated in clinical trials, limited real-world evidence is available on their impact on patient-reported outcomes (PROs) and the potential added value of wearable devices for continuous functional monitoring.ObjectivesTo evaluate the association between cladribine tablets use and PROs related to physical functioning and quality of life, and to explore the relationship between PROs and biometric data collected through wearable devices over 52 weeks in a real-world cohort of patients with highly active MS after therapeutic switch.MethodsCLADFIT-MS is a prospective, multicenter, observational phase IV study conducted in Italy. This interim analysis includes 190 patients with highly active MS who initiated cladribine tablets and had data available up to Week 52. PROs included the Multiple Sclerosis Impact Scale (MSIS-29), EuroQoL-5D-5L, and PROMIS-29 physical function and fatigue scores. Biometric data (e.g., range of movement, walking distance, sleep time) were collected using Fitbit® devices. Associations between PROs and wearable-derived data were analyzed using univariate mixed models and correlation matrices.ResultsMSIS-29 physical scores and EQ-5D-5L remained stable over 52 weeks. PROMIS-29 fatigue scores showed slight improvement [from 54.6 (9.59) to 51.8 (10.30)], while PROMIS-29 physical function scores remained stable. An exploratory association was observed between baseline range of movement and changes in MSIS-29 scores (p = 0.0425), and between walking distance and PROMIS-29 fatigue (p = 0.0345). Biometric variables demonstrated moderate to strong inter-correlations, suggesting internal consistency of the wearable-derived data.ConclusionIn this real-world cohort of patients with highly active MS, cladribine tablets treatment was associated with the maintenance of PROs over one year. The integration of wearable technology provided objective metrics that were consistent with patient perceptions, supporting the feasibility of combining digital tools with PROs to monitor functional outcomes in MS clinical practice.

Chronic exposure to trace metals has been increasingly recognized as a possible factor influencing the risk of amyotrophic lateral sclerosis (ALS). In the province of Catania, on the eastern slopes of Mount Etna, epidemiological investigations have highlighted the presence of a high-incidence cluster of the disease. Against this backdrop, the present study was designed to explore whether the concentrations of trace elements in cerebrospinal fluid (CSF) differ between ALS patients residing in this high-incidence area (In-Cluster) and those living in regions with lower incidence (Out-Cluster). For trace element analysis, CSF was analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Fourteen metals (Al, V, Mn, Co, Ni, Cu, Zn, As, Cd, Hg, Pb, Fe, Se, Mg) were quantified in standard and KED modes. No single metal concentration differed significantly between In-Cluster and Out-Cluster groups. However, In-Cluster patients frequently showed higher upper quartiles for Al, Mn, As, Hg, and Se, suggesting broader variability. Ratio analysis highlighted significant differences between groups, with higher Al/Cu ratios observed in In-Cluster patients. Sex-stratified analysis further revealed increased Mn-based ratios in females, with a significantly elevated Mn/Pb ratio. These patterns indicate possible dysregulation of trace metal homeostasis linked to environmental exposure. In conclusion, although statistical significance was limited, our findings suggest that chronic volcanic ash exposure may contribute to subtle imbalances between neurotoxic and neuroprotective elements in CSF, potentially influencing ALS susceptibility. Further studies integrating environmental monitoring, speciation analysis, and larger cohorts are needed to clarify the role of trace metals in ALS pathogenesis.

BACKGROUND AND OBJECTIVES:Children with multiple sclerosis (MS) are increasingly treated with high-efficacy monoclonal antibody therapies; however, treatment approaches vary widely, largely because of regulatory restrictions that often delay access until adulthood. We hypothesized that initiating these therapies during childhood confers greater benefits than their initiation in adulthood. This study, therefore, evaluated long-term disability in patients with pediatric-onset MS treated with monoclonal antibodies before age 18 compared with those who initiated these therapies in adulthood. METHODS:In this retrospective cohort study, patients younger than 18 years at the onset of MS symptoms were identified across 3 MS registries: MSBase, Observatoire Français de la Sclérose en Plaques, and the Italian MS Register. We categorized patients who commenced natalizumab, ocrelizumab, or rituximab between ages 12 and 17 into the pediatric high-efficacy therapy (HET) initiation group and those who began treatment between ages 20 and 22 into the adult HET initiation group. A landmark study design was used, with age 18 designated as the baseline and the outcome period spanning ages 23-27 years. The primary outcome was the change in Expanded Disability Status Scale (EDSS) scores, evaluated using a Bayesian weighted generalized linear mixed model. RESULTS:We included 277 patients (72% female), with a mean (SD) age at onset of MS symptoms of 14.97 (2.23) years. Of these, 108 initiated HET during childhood and 169 during adulthood. The postbaseline increase in EDSS scores was 0.53 steps lower in the pediatric HET initiation group compared with the adult group (β -0.53 [95% credible interval -0.87 to -0.19]). This benefit of pediatric HET initiation was most pronounced within the EDSS range of 4.5-6.0, with up to a 97% reduction in the odds of further disability worsening (odds ratio of EDSS score 5.0 over 4.5: 0.03 [95% credible interval 0.003-0.22]). DISCUSSION:Commencing high-efficacy monoclonal antibody therapy in childhood is associated with more favorable long-term disability outcomes than delayed initiation in adulthood. Early use of highly effective therapy is crucial for preserving neurologic function in children with MS. CLASSIFICATION OF EVIDENCE:This study provides Class II evidence that, in children aged 12-17 years with MS, initiating therapy with monoclonal antibodies before age 18 (vs 20-22) is associated with less disability accrual between the ages of 23 and 27.

INTRODUCTION:The incidence of multiple sclerosis (MS) has shown varying temporal trends across European countries in recent decades, particularly in high-incidence areas. We aimed to describe the incidence risks and temporal trends of MS in the city of Catania over the last 5 decades (1970-2019). METHODS:Incident cases of MS in residents in the city of Catania at disease onset were identified using the registries of the main MS centers. The annualized incidence risk was based on the year of clinical onset. RESULTS:From 1970 to 2019, a total of 754 incident cases were identified. The annualized incidence risk increased sharply from 0.7/100,000 in 1970-1974 to 9.2/100,000 in 2015-2019. The female-to-male ratio increased from 0.83 (95% CI: 0.26-2.62) in 1970-1974 to 2.14 (95% CI: 1.47-3.17) in 2015-2019. The mean age at onset was 29.1 ± 8.2 years in 1970-1974, reaching a mean of 37.1 ± 11.3 years in 2015-2019. CONCLUSION:Incidence of MS has been steadily increasing in the city of Catania, reaching a peak in 2015-2019 confirming Catania as one of the highest incidence areas in Italy. Additionally, we observed an increasing age at onset for both sexes, which may be attributable to improved diagnosis of late-onset MS cases.

BACKGROUND:Reproductive health is a critical component of care for women with multiple sclerosis (MS), yet standardized interdisciplinary approaches remain limited. OBJECTIVES:This Delphi consensus aimed to develop an interdisciplinary, evidence-informed care model tailored to the Italian healthcare system. RESULTS:A two-round Delphi process was conducted in Italy (June-July 2025), involving MS experts (Round 1: 107, Round 2: 95), including neurologists, gynecologists, pediatricians, nurses, and patient representatives. Participants evaluated key aspects of the reproductive care pathway, from preconception counseling to postpartum follow-up, to identify priorities and areas of agreement across disciplines. Strong consensus was achieved on the importance of early counseling, coordinated interdisciplinary management, and individualized treatment planning across the reproductive continuum. The central role of nurses in patient education was also emphasized. Divergence emerged regarding the continuation of specific therapies during pregnancy and the role of neonatal immunological monitoring following exposure to depleting agents, reflecting areas of ongoing uncertainty and limited evidence. CONCLUSIONS:This consensus proposes the first interdisciplinary framework for reproductive care in MS within the Italian context. It emphasizes patient-centered decision-making, collaboration across specialties, and the integration of reproductive health into routine MS management. By identifying both shared priorities and unresolved challenges, it provides a foundation for more harmonized, evidence-informed clinical practice and future research.

BACKGROUND:In multiple sclerosis (MS), real-world evidence supports early intensive treatment (EIT) with high-efficacy therapies (HET) over escalation (ESC), although comparative data on long-term safety across sequences remain limited. OBJECTIVE:To compare the incidence of infections and neoplasms in patients treated with different treatment sequences. METHODS:Data were extracted from the Italian MS and Related Disorders Register. DMTs were classified as moderate-efficacy treatment (MET), continuous HET (C-HET) or pulsed HET (P-HET). Six therapeutic sequences were reconstructed: MET-only, C-HET-only, P-HET-only, MET→C-HET, MET→P-HET and P-HET→MET. Incidence rates (IRs; per 1000 person-years) and incidence rate ratios (IRRs) were estimated using multivariable Poisson regression, adjusting for age, sex, Expanded Disability Status Scale (EDSS), disease duration, MS phenotype and prior relapse activity. RESULTS:A total of 37,375 patients were included in the analysis, with a median duration of treatment exposure of 8.8 years. Infection risk was significantly higher with C-HET-only (IR, 24.82; IRR, 3.12), P-HET-only (IR, 13.43; IRR, 1.69), MET→C-HET (IR, 10.46; IRR, 1.32) and MET→P-HET (IR, 12.30; IRR, 1.55) versus MET-only (IR, 7.94), while P-HET→MET showed no significant difference from MET-only (IR, 7.67; IRR, 0.97). Regarding neoplasm incidence, P-HET-only showed the lowest rates (IR, 0.18; IRR, 0.24), whereas it was significantly higher in C-HET-only (IR, 1.33; IRR, 1.79) and MET→C-HET (IR, 1.01; IRR, 1.36) versus MET-only (IR, 0.74). CONCLUSIONS:This is the first real-world study to compare the safety of different sequences in a national registry. ESC strategies did not confer a long-term safety advantage over EIT. Among HET regimens, C-HET was associated with the greatest risk of both serious infections and neoplasms, whereas P-HET showed the lowest neoplasm incidence.

Multiple Sclerosis (MS) severity is influenced by several factors. Understanding the impact of age at disease onset may help to better characterize clinical and disease features across age groups. This study aimed to characterize the clinical features and disability outcomes of late-onset MS (LOMS) and very late-onset MS (vLOMS), compared to adult-onset MS (AOMS). We conducted an observational study using data from the MSBase registry and categorized patients based on age at MS onset: AOMS (18–39 years), transition onset (40–49 years), LOMS (50–59 years), and vLOMS (≥ 60 years). Disease progression was assessed using the 24 week confirmed disability progression, EDSS4 and 6 milestones, conversion to secondary progressive MS(SPMS), and the first progression independent of relapse activity (PIRA) event. Cox proportional hazard regression models were used to determine unadjusted hazard ratios(HR), and propensity score inverse probability of treatment weighting(PS-IPTW) balanced covariate distributions. Among 81,236 patients, 5.2

Objective: Hereditary spastic paraplegia (HSP) is a group of disorders characterized by progressive spasticity and lower limb weakness, with mutations in SPG4/SPAST being the most common cause. Detailed studies and clinical and molecular comparisons across different populations are missing. We examined the clinical, pathological, and genetic spectrum of the SPG4/SPAST gene in patients with HSP. Methods: The study involved 726 HSP patients recruited from Italy, Brazil, and Japan between 2001 and 2025, with analysis conducted in collaborative centers. SPG4/SPAST variants were identified using direct and next-generation sequencing. The pathogenicity of novel variants was confirmed through familial segregation and in silico analysis. Results: Clinical and epidemiological differences were observed across populations, particularly in phenotype, age at onset, and disability, expanding the SPG4 clinical spectrum. Genetic analysis identified 52 pathogenic SPG4/SPAST mutations in 284 patients, including four novel variants. Several mutations were population-specific, and a possible founder effect was suggested for a recurrent variant in Italy. Dementia occurred in 44 HSP-SPG4 patients and was neuropathologically confirmed in four unrelated autopsied cases from four families comprising 28 individuals; atypical pathological features were observed in all four autopsied cases. Additionally, 18 patients with SPG4/SPAST mutations presented with thin corpus callosum and intellectual disability. Interpretation: In this study, we investigated pathogenic SPG4/SPAST variants in an international cohort of HSP patients from three continents. Our findings expand the clinical spectrum of HSP-SPG4, identifying a new type complicated by an atypical pathological form of dementia. Careful assessment of genotype-phenotype relationships offers insights into patient counseling and future research planning.

BACKGROUND AND OBJECTIVE:As more people with multiple sclerosis (MS) survive cancer, questions about MS management after cancer are increasingly relevant. This study aimed to describe post-cancer treatment patterns and MS outcomes in people with recorded chemotherapy exposure. METHODS:Using MSBase, we identified people with MS with cancer and chemotherapy exposure. Time to first relapse and 6-month confirmed disability progression (CDP) were analysed using Cox models with disease-modifying therapy (DMT) as a time-varying covariate. Outcomes were contextualised using 1:2 propensity-matched MS controls without cancer or chemotherapy. RESULTS:In total, 363 individuals were followed for 2.8 years (median) after cancer. Older age at cancer was associated with lower relapse hazard (hazard ratio (HR) = 0.96 per year, p = 0.008), while DMT category was not. The DMT category was not associated with CDP. In matched analysis (256 vs. 505), relapse hazard was lower during the first year after cancer (HR = 0.30, p = 0.015) with no difference thereafter; CDP risk was similar (HR = 1.13, p = 0.60). CONCLUSION:Post-cancer DMT category was not associated with relapse or CDP. Lower first-year relapse hazard, together with lower relapse hazard at older age, may provide cautious reassurance regarding early post-cancer inflammatory activity in similar clinical contexts, although the drivers of the first-year signal remain uncertain.

BACKGROUND:The ConCure-SM intervention [ISRCTN48527663] consists of an advance care planning (ACP) training program for neurologists/other professionals caring for people with progressive multiple sclerosis (PwPMS). We assessed the communication competences of ACP-trained neurologists who participated in the trial. METHODS:Eighteen ACP conversations were audio-recorded. After each conversation, participants (PwPMS, significant others [SOs], and neurologists) rated the neurologist's communication skills using dedicated versions of the Quality of Communication questionnaire (QOC). Independent observers assessed the conversations using the Observing Patient Involvement in Shared Decision Making (SDM; OPTION), and the Verona Coding Definitions of Emotional Sequences (VR-CoDES). RESULTS:Mean duration of the ACP conversations was 62.7 minutes. Neurologists (5/7 women) were 30-62-year-old. PwPMS mean age was 61.8 years, 39% were women. Mean QOC scores (distinguished in general communication and end-of-life communication; 0-100 scale) were 92.4, 90.1 respectively, according to PwPMS; 95.2, 94.3 according to SOs. Mean neurologists' self-reported QOC score (0-100 scale) was 69.5. Mean OPTION score (0-100 scale) was 48.4. PwPMS expressed a median of 8.5 cues (hints to emotion) and 3.0 concerns (explicit expressions of emotion) per conversation. Neurologists provided space to 59% of cues and 73% of concerns. A quarter of cues/concerns contained figurative expressions or metaphors to express concerns or as signals of emotional distress. Moreover, 12% of expressions were coded as positive emotional statements (i.e., expressions indicating hope, confidence, and positive wishes). CONCLUSIONS:Neurologists' communication skills during ACP conversations were rated as high using the QOC by both PwPMS and SOs, while neurologists rated their own skills more critically. Neurologists' SDM competences were moderate, but higher compared to two published studies on MS consultations. Qualitative and quantitative analysis of ACP conversation transcripts indicate that ACP can evoke many emotions. In most instances neurologists provided space for the PwPMS to elaborate on affective expressions. TRIAL REGISTRATION:ISRCTN48527663.

In the treatment of relapsing-remitting multiple sclerosis, autologous haematopoietic stem cell transplant (AHSCT) and immune-reconstitution therapies show several similarities. These treatment strategies have not yet been compared head-to-head. This study emulated pairwise trials of comparative effectiveness of stem cell transplant versus immune-reconstitution therapies cladribine and alemtuzumab. This cohort/registry study of comparative treatment effectiveness included data from seven specialist multiple sclerosis centres with AHSCT programmes (RESCUE-MS) and international MSBase registry during 2006-2023. The study included patients with relapsing-remitting multiple sclerosis treated with AHSCT, cladribine or alemtuzumab, with a minimum of 2-months follow-up before commencing study therapy and ≥2 disability assessments after commencing the study therapy. Patients were matched on a propensity score derived from their clinical and demographic characteristics. The matched groups were compared according to annualized relapse rates, freedom from relapses and 6-month confirmed disability worsening and improvement (measured with the Expanded Disability Status Scale). The matching of 143 (stem cell) to 283 cladribine-treated patients and 134 (stem cell) to 562 alemtuzumab-treated patients reduced the measured differences between the groups by 98% and 96%, respectively. The matched patients had high mean disease activity (>0.8 relapses in the prior 2 years), mean Expanded Disability Status Scale scores of 3-4, and were followed-up for a mean of 3.8-3.9 (stem cell), 1.9 (cladribine) or 4.5 years (alemtuzumab). Compared with cladribine, stem cell transplant was associated with a lower risk of relapse [mean annualized relapse rate ± standard deviation (SD): 0.05 ± 0.28 versus 0.16 ± 0.39, respectively; hazard ratio: 0.24; 95% confidence interval (CI): 0.15-0.41], similar risk of disability worsening (hazard ratio: 0.70; 95% CI: 0.34-1.43) and higher probability of disability improvement (hazard ratio: 2.19; 95% CI: 1.31-3.66). Compared with alemtuzumab, stem cell transplant was associated with a lower risk of relapses (mean annualized relapse rate ± SD: 0.04 ± 0.23 versus 0.09 ± 0.21, respectively; hazard ratio: 0.52; 95% CI: 0.29-0.93), similar risk of disability worsening (hazard ratio: 0.95; 95% CI: 0.53-1.72) and higher probability of disability improvement (hazard ratio: 2.03; 95% CI: 1.23-3.34). Thirty-four per cent of patients treated with stem cell transplant experienced delayed complications, mainly infections. No treatment-associated deaths were reported. Among patients with active relapsing-remitting multiple sclerosis and moderate disability, AHSCT is superior to cladribine and alemtuzumab at suppressing relapses and enabling recovery of neurological function. The high effectiveness of stem cell transplant is likely attributable to a complex interplay between immune suppression and reconstitution.

Anti-JC virus (JCV) antibody testing is central to progressive multifocal leukoencephalopathy (PML) risk stratification in patients treated with natalizumab. While STRATIFY JCV™ is the historical reference assay, IMMUNOWELL™ is increasingly used in the context of biosimilar adoption. We aimed to determine whether inter-assay discordance reflects true biological divergence or threshold-dependent interpretative effects within clinically relevant PML risk categories. In this single-center observational study, 250 consecutive patients with relapsing multiple sclerosis (RMS) underwent same-day paired STRATIFY and IMMUNOWELL testing. Agreement was evaluated under two interpretative frameworks: (i) manufacturer-defined analytical cutoffs and (ii) clinically adopted PML risk-based thresholds. Quantitative comparability was assessed using Pearson correlation and Bland–Altman analysis. Using analytical cutoffs, concordance was 78.0

Background:Two principal methods for detecting anti-John Cunningham virus (JCV) antibodies are currently utilized in clinical practice: STRATIFY JCV™, an ELISA developed by Biogen, and IMMUNOWELL™, a solid-phase ELISA assay by Polpharma Biologics/GenBio. Objective:We aimed to evaluate the concordance between STRATIFY and IMMUNOWELL in detecting anti-JCV antibodies in a real-world population of patients with relapsing-remitting multiple sclerosis (RRMS) undergoing natalizumab therapy. Design:This monocentric observational study screened all patients treated with natalizumab for at least 6 months, referring to the MS Center of the University Hospital of Catania. Methods:Each patient's serum was tested simultaneously using STRATIFY-2 (STRATIFY JCV DxSelect) and IMMUNOWELL assays. The qualitative results (positive/negative) were compared, and the index values were analyzed using Pearson's correlation and Bland-Altman plots. Inter-method agreement was calculated using Cohen's kappa coefficient. Results:Among the 120 patients tested, 82 were positive and 31 negative with both STRATIFY and IMMUNOWELL. Four cases were STRATIFY-negative but IMMUNOWELL-positive, and three were the opposite. Overall concordance was 94.2%, with a Cohen's Kappa of 0.86, indicating strong agreement. The index values showed strong correlation (Pearson r = 0.79, p < 0.001) and the coefficient of determination (r 2) was 0.62. Conclusion:STRATIFY and IMMUNOWELL demonstrate a high level of agreement in the detection of anti-JCV antibodies in patients with RRMS receiving natalizumab. IMMUNOWELL may serve as a reliable complementary method, especially in cases where borderline serostatus could influence therapeutic strategy. Regular and accurate monitoring of JCV status remains essential for guiding long-term treatment safety and optimizing individual patient outcomes.