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BACKGROUND AND PURPOSE: Treatment persistence is the continuation of therapy over time. It reflects a combination of treatment efficacy and tolerability. We aimed to describe real-world rates of persistence on disease-modifying therapies (DMTs) for people with multiple sclerosis (pwMS) and reasons for DMT discontinuation. METHODS: Treatment data on 4366 consecutive people with relapse-onset multiple sclerosis (MS) were pooled from 13 UK specialist centres during 2021. Inclusion criteria were exposure to at least one MS DMT and a complete history of DMT prescribing. PwMS in blinded clinical trials were excluded. Data collected included sex, age at MS onset, age at DMT initiation, DMT treatment dates, and reasons for stopping or switching DMT. For pwMS who had received immune reconstituting therapies (cladribine/alemtuzumab), discontinuation date was defined as starting an alternative DMT. Kaplan-Meier survival analyses were used to express DMT persistence. RESULTS: In 6997 treatment events (1.6 per person with MS), median time spent on any single maintenance DMT was 4.3 years (95% confidence interval = 4.1-4.5 years). The commonest overall reasons for DMT discontinuation were adverse events (35.0%) and lack of efficacy (30.3%). After 10 years, 20% of people treated with alemtuzumab had received another subsequent DMT, compared to 82% of people treated with interferon or glatiramer acetate. CONCLUSIONS: Immune reconstituting DMTs may have the highest potential to offer a single treatment for relapsing MS. Comparative data on DMT persistence and reasons for discontinuation are valuable to inform treatment decisions and in personalizing treatment in MS.
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Esclerosis Múltiple Recurrente-Remitente , Humanos , Masculino , Femenino , Adulto , Persona de Mediana Edad , Esclerosis Múltiple Recurrente-Remitente/tratamiento farmacológico , Esclerosis Múltiple/tratamiento farmacológico , Cumplimiento de la Medicación/estadística & datos numéricos , Factores Inmunológicos/uso terapéuticoRESUMEN
OBJECTIVES: The objective of this study was to model multiple sclerosis (MS) disease progression and compare disease trajectories by sex, age of onset, and year of diagnosis. STUDY DESIGN AND SETTING: Longitudinal EDSS scores (20,854 observations) were collected for 1,787 relapse-onset MS patients at MS clinics in South Wales and modelled using a multilevel model (MLM). The MLM adjusted for covariates (sex, age of onset, year of diagnosis, and disease-modifying treatments), and included interactions between baseline covariates and time variables. RESULTS: The optimal model was truncated at 30 years after disease onset and excluded EDSS recorded within 3 months of relapse. As expected, older age of onset was associated with faster disease progression at 15 years (effect size (ES): 0.75; CI: 0.63, 0.86; p: <0.001) and female-sex progressed more slowly at 15 years (ES: -0.43; CI: -0.68, -0.18; p: <0.001). Patients diagnosed more recently (defined as 2007-2011 and >2011) progressed more slowly than those diagnosed historically (<2006); (ES: -0.46; CI: -0.75, -0.16; p: 0.006) and (ES: -0.95; CI: -1.20, -0.70; p: <0.001), respectively. CONCLUSION: We present a novel model of MS outcomes, accounting for the non-linear trajectory of MS and effects of baseline covariates, validating well-known risk factors (sex and age of onset) associated with disease progression. Also, patients diagnosed more recently progressed more slowly than those diagnosed historically.
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Edad de Inicio , Progresión de la Enfermedad , Esclerosis Múltiple , Humanos , Masculino , Femenino , Adulto , Esclerosis Múltiple/epidemiología , Persona de Mediana Edad , Gales/epidemiología , Estudios de Cohortes , Estudios Longitudinales , Factores Sexuales , Adulto JovenRESUMEN
A multiple sclerosis (MS) prodrome has recently been described and is characterised by increased rates of healthcare utilisation and an excess frequency of fatigue, bladder problems, sensory symptoms and pain, in the years leading up to clinical onset of disease. This important observation may have several potential applications including in the identification of risk factors for disease, the potential to delay or prevent disease onset and early opportunities to alter disease course. It may also offer possibilities for the use of risk stratification algorithms and effective population screening. If standardised, clearly defined and disease specific, an MS prodrome is also likely to have a profound influence on research and clinical trials directed at the earliest stages of disease. In order to achieve these goals, it is essential to consider experience already gleaned from other disorders. More specifically, in some chronic neurological disorders the understanding of disease pro-drome is now well advanced and has been successfully applied. However, understanding of the MS prodrome remains at an early stage with key questions including the length of the prodrome, symptom specificity and potential benefits of early intervention as yet unanswered. In this review we will explore the evidence available to date and suggest future research strategies to address unanswered questions. In addition, whilst current understanding of the MS prodrome is not yet sufficient to justify changes in public health policy or MS management, we will consider the practical utility and future application of the MS prodrome in a wider health care setting.
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Esclerosis Múltiple , Humanos , Esclerosis Múltiple/epidemiología , Factores de Riesgo , Progresión de la Enfermedad , Fatiga/etiología , Síntomas ProdrómicosRESUMEN
OBJECTIVE: Currently, 233 genetic loci are known to be associated with susceptibility to multiple sclerosis (MS). Two independent pivotal severity genome-wide association studies recently found the first genome-wide significant single-nucleotide variant (SNV; rs10191329A ) and several other suggestive loci associated with overall disability outcomes. It is now important to understand if these findings can influence individual patient management. METHODS: We assessed whether these progression SNVs are associated with detailed clinical phenotypes in a well-characterized prospective cohort of 1,455 MS patients. We used logistic regression, survival analysis, and propensity score matching to predict relevant long-term clinical outcomes. RESULTS: We were unable to detect any association between rs10191329A and a range of clinically relevant outcomes (eg, time to Expanded Disability Status Scale milestones, age-related MS severity score, anatomical localization at onset or during subsequent relapses, annualized relapse rate). In addition, an extremes of outcome case-control analysis using a propensity score matching for genotype detected no association between disease severity and rs10191329A . However, we were able to replicate the association of two suggestive SNVs (rs7289446G and rs868824C ) with the development of fixed disability, albeit with modest effect sizes, and the association of HLA-DRB1*1501 with age at onset. INTERPRETATION: Identification of rs10191329A and other suggestive SNVs are of considerable importance in understanding pathophysiological processes associated with MS severity. However, it is unlikely that individual genotyping can currently be used in a clinical setting to guide disease management. This study shows the importance of independent replication of genome-wide association studies associated with disease progression in neurodegenerative disorders. ANN NEUROL 2024;95:459-470.
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Esclerosis Múltiple , Humanos , Esclerosis Múltiple/genética , Estudios Prospectivos , Estudio de Asociación del Genoma Completo , Genotipo , Fenotipo , Progresión de la EnfermedadRESUMEN
BACKGROUND: People with multiple sclerosis (pwMS) treated with certain disease-modifying therapies (DMTs) have attenuated IgG response following COVID-19 vaccination; however, the clinical consequences remain unclear. OBJECTIVE: To report COVID-19 rates in pwMS according to vaccine serology. METHODS: PwMS with available (1) serology 2-12 weeks following COVID-19 vaccine 2 and/or vaccine 3 and (2) clinical data on COVID-19 infection/hospitalisation were included. Logistic regression was performed to examine whether seroconversion following vaccination predicted risk of subsequent COVID-19 infection after adjusting for potential confounders. Rates of severe COVID-19 (requiring hospitalisation) were also calculated. RESULTS: A total of 647 pwMS were included (mean age 48 years, 500 (77%) female, median Expanded Disability Status Scale (EDSS) 3.5% and 524 (81%) exposed to DMT at the time of vaccine 1). Overall, 472 out of 588 (73%) were seropositive after vaccines 1 and 2 and 222 out of 305 (73%) after vaccine 3. Seronegative status after vaccine 2 was associated with significantly higher odds of subsequent COVID-19 infection (odds ratio (OR): 2.35, 95% confidence interval (CI): 1.34-4.12, p = 0.0029), whereas seronegative status after vaccine 3 was not (OR: 1.05, 95% CI: 0.57-1.91). Five people (0.8%) experienced severe COVID-19, all of whom were seronegative after most recent vaccination. CONCLUSION: Attenuated humoral response to initial COVID-19 vaccination predicts increased risk of COVID-19 in pwMS, but overall low rates of severe COVID-19 were seen.
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Vacunas contra la COVID-19 , COVID-19 , Esclerosis Múltiple , Femenino , Humanos , Masculino , Persona de Mediana Edad , COVID-19/epidemiología , COVID-19/prevención & control , Vacunas contra la COVID-19/efectos adversos , Hospitalización , Esclerosis Múltiple/tratamiento farmacológico , Esclerosis Múltiple/epidemiología , VacunaciónRESUMEN
The median survival time of newly-diagnosed MS patients without severe disabilities is approximately 30-35 years. The prognosis after the onset of severe disability has not been reported. Based on Harding et al.'s 2018 study of the Southeast Wales MS registry, we calculated life expectancies according to the Expanded Disability Status Scale (EDSS). Upon loss of independent ambulation (EDSS 6-6.5; mean age 51.2) life expectancy was 13.3 additional years. At EDSS 9-9.5 (mean age 70.8) life expectancy was 1.1 additional years. These figures provide an empirical basis for discussions of advanced MS care planning.
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Personas con Discapacidad , Esclerosis Múltiple , Humanos , Persona de Mediana Edad , Anciano , Esclerosis Múltiple/diagnóstico , Esperanza de Vida , Sistema de Registros , Gales , Evaluación de la DiscapacidadRESUMEN
BACKGROUND: People with MS treated with anti-CD20 therapies and fingolimod often have attenuated responses to initial COVID-19 vaccination. However, uncertainties remain about the benefit of a 3rd (booster) COVID-19 vaccine in this group. METHODS: PwMS without a detectable IgG response following COVID-19 vaccines 1&2 were invited to participate. Participants provided a dried blood spot +/- venous blood sample 2-12 weeks following COVID-19 vaccine 3. Humoral and T cell responses to SARS-CoV-2 spike protein and nucleocapsid antigen were measured. RESULTS: Of 81 participants, 79 provided a dried blood spot sample, of whom 38 also provided a whole blood sample; 2 provided only whole blood. Anti-SARS-CoV-2-spike IgG seroconversion post-COVID-19 vaccine 3 occurred in 26/79 (33%) participants; 26/40 (65%) had positive T-cell responses. Overall, 31/40 (78%) demonstrated either humoral or cellular immune response post-COVID-19 vaccine 3. There was no association between laboratory evidence of prior COVID-19 and seroconversion following vaccine 3. CONCLUSIONS: Approximately one third of pwMS who were seronegative after initial COVID-19 vaccination seroconverted after booster (third) vaccination, supporting the use of boosters in this group. Almost 8 out of 10 had a measurable immune response following 3rd COVID-19 vaccine.
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COVID-19 , Esclerosis Múltiple , Anticuerpos Antivirales , COVID-19/prevención & control , Vacunas contra la COVID-19 , Humanos , Inmunoglobulina G , Esclerosis Múltiple/tratamiento farmacológico , SARS-CoV-2 , Glicoproteína de la Espiga del Coronavirus , VacunaciónRESUMEN
OBJECTIVE: The purpose of this study was to investigate the effect of disease modifying therapies on immune response to severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) vaccines in people with multiple sclerosis (MS). METHODS: Four hundred seventy-three people with MS provided one or more dried blood spot samples. Information about coronavirus disease 2019 (COVID-19) and vaccine history, medical, and drug history were extracted from questionnaires and medical records. Dried blood spots were eluted and tested for antibodies to SARS-CoV-2. Antibody titers were partitioned into tertiles with people on no disease modifying therapy as a reference. We calculated the odds ratio of seroconversion (univariate logistic regression) and compared quantitative vaccine response (Kruskal Wallis) following the SARS-CoV-2 vaccine according to disease modifying therapy. We used regression modeling to explore the effect of vaccine timing, treatment duration, age, vaccine type, and lymphocyte count on vaccine response. RESULTS: Compared to no disease modifying therapy, the use of anti-CD20 monoclonal antibodies (odds ratio = 0.03, 95% confidence interval [CI] = 0.01-0.06, p < 0.001) and fingolimod (odds ratio = 0.04; 95% CI = 0.01-0.12) were associated with lower seroconversion following the SARS-CoV-2 vaccine. All other drugs did not differ significantly from the untreated cohort. Both time since last anti-CD20 treatment and total time on treatment were significantly associated with the response to the vaccination. The vaccine type significantly predicted seroconversion, but not in those on anti-CD20 medications. Preliminary data on cellular T-cell immunity showed 40% of seronegative subjects had measurable anti-SARS-CoV-2 T cell responses. INTERPRETATION: Some disease modifying therapies convey risk of attenuated serological response to SARS-CoV-2 vaccination in people with MS. We provide recommendations for the practical management of this patient group. ANN NEUROL 20219999:n/a-n/a.
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Antirreumáticos/uso terapéutico , Vacunas contra la COVID-19/inmunología , COVID-19/prevención & control , Huésped Inmunocomprometido , Esclerosis Múltiple/inmunología , Seroconversión/efectos de los fármacos , Adulto , Anticuerpos Antivirales/sangre , Anticuerpos Antivirales/efectos de los fármacos , Femenino , Humanos , Masculino , Persona de Mediana Edad , Esclerosis Múltiple/tratamiento farmacológico , SARS-CoV-2 , Reino UnidoRESUMEN
BACKGROUND: Non-motor symptoms are well established phenotypic components of adult-onset idiopathic, isolated, focal cervical dystonia (AOIFCD). However, improved understanding of their clinical heterogeneity is needed to better target therapeutic intervention. Here, we examine non-motor phenotypic features to identify possible AOIFCD subgroups. METHODS: Participants diagnosed with AOIFCD were recruited via specialist neurology clinics (dystonia wales: n = 114, dystonia coalition: n = 183). Non-motor assessment included psychiatric symptoms, pain, sleep disturbance, and quality of life, assessed using self-completed questionnaires or face-to-face assessment. Both cohorts were analyzed independently using Cluster, and Bayesian multiple mixed model phenotype analyses to investigate the relationship between non-motor symptoms and determine evidence of phenotypic subgroups. RESULTS: Independent cluster analysis of the two cohorts suggests two predominant phenotypic subgroups, one consisting of approximately a third of participants in both cohorts, experiencing increased levels of depression, anxiety, sleep impairment, and pain catastrophizing, as well as, decreased quality of life. The Bayesian approach reinforced this with the primary axis, which explained the majority of the variance, in each cohort being associated with psychiatric symptomology, and also sleep impairment and pain catastrophizing in the Dystonia Wales cohort. CONCLUSIONS: Non-motor symptoms accompanying AOIFCD parse into two predominant phenotypic sub-groups, with differences in psychiatric symptoms, pain catastrophizing, sleep quality, and quality of life. Improved understanding of these symptom groups will enable better targeted pathophysiological investigation and future therapeutic intervention.
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Trastornos Distónicos , Tortícolis , Adulto , Teorema de Bayes , Humanos , Fenotipo , Calidad de Vida , Tortícolis/epidemiologíaRESUMEN
BACKGROUND: Prognostication in multiple sclerosis (MS) remains challenging. Biomarkers capable of providing this information at diagnosis would be valuable in shaping therapeutic decisions. Measurement of neurofilament light (NfL) has shown promise in predicting clinical outcomes in established MS, but its ability to predict outcomes in real-world cohorts at diagnosis requires further validation. METHODS: We used linear regression to evaluate the relationship between serum NfL (sNfL), measured at the time of diagnosis with short-term (1-year) and medium-term (5-year) clinical outcomes in 164 people with MS from a real-world, population-based cohort. Cox proportional hazards regression was used to analyse the association between sNfL and subsequent hazard of relapse or sustained accumulation of disability (SAD). Analyses were adjusted for age and disease-modifying treatment (DMT). RESULTS: sNfL concentration at diagnosis was modestly associated with baseline EDSS score (ß = 0.272, 95% CI 0.051 to 0.494, p = 0.016). However, no significant associations were found between baseline sNfL and odds of relapse at 12-months, 5-year EDSS change, or the hazard of relapse or SAD over 5 years follow-up. Dichotomising baseline sNfL according to the median sNfL did not change these findings. CONCLUSIONS: sNfL appears to be of limited clinical utility in predicting future irreversible neurological disability in a largely untreated real-world population, and remains insufficiently validated to shape treatment decisions at the time of diagnosis. Further studies may be needed for sNfL to be considered as a prognostic marker in the MS clinic. However the masking effect of DMTs on the natural disease trajectory will continue to pose challenges.
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Filamentos Intermedios , Esclerosis Múltiple , Biomarcadores , Estudios de Cohortes , Humanos , Esclerosis Múltiple/diagnóstico , Esclerosis Múltiple/epidemiología , Esclerosis Múltiple/terapia , Proteínas de Neurofilamentos , RecurrenciaRESUMEN
BACKGROUND: As disease-modifying therapies become approved for primary progressive multiple sclerosis (PPMS), services must be aligned in readiness. METHODS: In this paper we use population and clinic-based data to estimate eligibility rates for ocrelizumab, and the extent of additional service requirements necessary to ensure its widespread introduction in PPMS. RESULTS: Overall population estimates for the incidence and prevalence of people with PPMS who are eligible for ocrelizumab are 1.6 and 4.2 per 100,000 respectively. The majority (87%) of incident cases of PPMS satisfied clinical eligibility criteria for ocrelizumab but lacked radiological evidence of disease activity due to a historical tendency not to routinely monitor using MRI in this group. The majority of prevalent patients did not satisfy clinical eligibility criteria for ocrelizumab, mainly because of advanced disease duration or disability. CONCLUSIONS: These findings illustrate the fact that there has been a tendency for people with PPMS not to receive routine clinical and radiological monitoring. Additional planning or resources will be required to facilitate contemporary disease re-evaluation and surveillance at a population level.
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Anticuerpos Monoclonales Humanizados/uso terapéutico , Personas con Discapacidad , Determinación de la Elegibilidad , Utilización de Instalaciones y Servicios , Factores Inmunológicos/uso terapéutico , Esclerosis Múltiple Crónica Progresiva/diagnóstico por imagen , Esclerosis Múltiple Crónica Progresiva/tratamiento farmacológico , Sistema de Registros , Adulto , Anciano , Estudios de Cohortes , Personas con Discapacidad/estadística & datos numéricos , Determinación de la Elegibilidad/estadística & datos numéricos , Utilización de Instalaciones y Servicios/estadística & datos numéricos , Femenino , Humanos , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Esclerosis Múltiple Crónica Progresiva/epidemiología , Sistema de Registros/estadística & datos numéricos , Reino Unido/epidemiologíaRESUMEN
OBJECTIVE: To examine the association between socioeconomic status (SES) and disability outcomes and progression in multiple sclerosis (MS). METHODS: Health administrative and MS clinical data were linked for 2 cohorts of patients with MS in British Columbia (Canada) and South East Wales (UK). SES was measured at MS symptom onset (±3 years) based on neighborhood-level average income. The association between SES at MS onset and sustained and confirmed Expanded Disability Status Scale (EDSS) 6.0 and 4.0 and onset of secondary progression of MS (SPMS) were assessed using Cox proportional hazards models. EDSS scores were also examined via linear regression, using generalized estimating equations (GEE) with an exchangeable working correlation. Models were adjusted for onset age, sex, initial disease course, and disease-modifying drug exposure. Random effect models (meta-analysis) were used to combine results from the 2 cohorts. RESULTS: A total of 3,113 patients with MS were included (2,069 from Canada; 1,044 from Wales). A higher SES was associated with a lower hazard of reaching EDSS 6.0 (adjusted hazard ratio [aHR] 0.90, 95% confidence interval [CI] 0.89-0.91), EDSS 4.0 (aHR 0.93, 0.88-0.98), and SPMS (aHR 0.94, 0.88-0.99). The direction of findings was similar when all EDSS scores were included (GEE: ß = -0.13, -0.18 to -0.08). CONCLUSIONS: Lower neighborhood-level SES was associated with a higher risk of disability progression. Reasons for this association are likely to be complex but could include factors amenable to modification, such as lifestyle or comorbidity. Our findings are relevant for planning and development of MS services.
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Esclerosis Múltiple/fisiopatología , Clase Social , Adulto , Colombia Británica , Progresión de la Enfermedad , Femenino , Humanos , Masculino , Persona de Mediana Edad , Pronóstico , Modelos de Riesgos Proporcionales , Estudios Prospectivos , Gales , Adulto JovenRESUMEN
The complement pathway has potential contributions to both white (WM) and grey matter (GM) pathology in Multiple Sclerosis (MS). A quantitative assessment of complement involvement is lacking. Here we describe the use of Tissue MicroArray (TMA) methodology in conjunction with immunohistochemistry to investigate the localization of complement pathway proteins in progressive MS cortical GM and subcortical WM. Antibodies targeting complement proteins C1q, C3b, regulatory proteins C1 inhibitor (C1INH, complement receptor 1 (CR1), clusterin, factor H (FH) and the C5a anaphylatoxin receptor (C5aR) were utilised alongside standard markers of tissue pathology. All stained slides were digitised for quantitative analysis. We found that numbers of cells immunolabelled for HLA-DR, GFAP, C5aR, C1q and C3b were increased in WM lesions (WML) and GM lesions (GML) compared to normal appearing WM (NAWM) and GM (NAGM), respectively. The complement regulators C1INH, CR1, FH and clusterin were more abundant in WM lesions, while the number of C1q+ neurons were increased and the number of C1INH+, clusterin+, FH+ and CR1+ neurons decreased in GM lesions. The number of complement component positive cells (C1q, C3b) correlated with complement regulator expression in WM, but there was no statistical association between complement activation and regulator expression in the GM. We conclude that TMA methodology and quantitative analysis provides evidence of complement dysregulation in MS GML, including an association of the numerical density of C1q+ cells with tissue lesions. Our work confirms that complement activation and dysregulation occur in all cases of progressive MS and suggest that complement may provide potential biomarkers of the disease.
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Encéfalo/inmunología , Activación de Complemento , Esclerosis Múltiple/inmunología , Análisis de Matrices Tisulares/métodos , Adulto , Anciano , Astrocitos/inmunología , Astrocitos/patología , Encéfalo/patología , Femenino , Sustancia Gris/inmunología , Sustancia Gris/patología , Humanos , Inmunohistoquímica , Riñón/inmunología , Riñón/patología , Masculino , Microglía/inmunología , Microglía/patología , Persona de Mediana Edad , Esclerosis Múltiple/patología , Neuronas/inmunología , Neuronas/patología , Sustancia Blanca/inmunología , Sustancia Blanca/patologíaRESUMEN
BACKGROUND: Multiple sclerosis (MS) relapses contribute to disability and influence treatment decisions. Many centres now provide open access to specialist services for patients with new symptoms. However, there is scarce literature on the spectrum of presentations encountered in this setting. OBJECTIVE: The objective of this paper is to characterise presentations to an open, rapid-access MS relapse clinic and the impact on disease management. METHODS: A retrospective review of outpatient episodes over a three-year period was conducted. Demographic and service data, symptoms, disability, diagnosis and management were recorded according to a standardised proforma. RESULTS: A total of 371 attendances were analysed. A new MS relapse was diagnosed in 216 (58%) episodes, of which 56 (26%) patients had an additional diagnosis which had also contributed to their presentation. Of 266 reports of non-relapse-related symptoms, 73 were unrelated to MS. Treatment interventions were made in almost all relapsing patients and in 70% of patients presenting with acute, non-relapse-related symptoms of MS. Changes to disease-modifying therapies were considered in 28% of consultations. CONCLUSION: Diagnosing MS relapses is crucial for disease management and yet remains challenging. Clinicians should be aware of differential diagnoses and confounding factors. The high incidence of therapeutic interventions observed suggests that rapid-access clinics represent an effective platform for responsive disease management.
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Progresión de la Enfermedad , Esclerosis Múltiple/fisiopatología , Índice de Severidad de la Enfermedad , Adulto , Femenino , Estudios de Seguimiento , Humanos , Masculino , Persona de Mediana Edad , Esclerosis Múltiple/terapia , RecurrenciaRESUMEN
BACKGROUND: A minority of patients with multiple sclerosis (MS) have primary progressive disease (PPMS). Treatment options are currently limited, but as prospects for interventional studies become more realistic, understanding contemporary outcome data will be key to successful trial design. METHODS: 234 PPMS patients were identified from a population-based cohort of 2131 (11.0%) and mean follow-up of 13.1â years. Time to established disability endpoints was compared with patients with relapsing-onset MS (ROMS) using survival analysis, and Cox regression employed to explore factors contributing to disability accumulation. Results were used to create predictive power models for clinical trials in PPMS. RESULTS: Time to fixed disability milestones was shorter than in ROMS (Expanded Disability Status Scale (EDSS) 4.0:8.1 vs. 17.1â years, p<0.001; EDSS 6.0: 9.6 vs. 22.1â years, p<0.001; EDSS 8.0: 20.7 vs. 39.7â years, p<0.001), but there were no differences in age-related disability. Age and cerebellar symptoms at onset affected rate of progression. Modelling of these data indicated that trials employing EDSS change of 1.0 as the primary outcome measure would be powered to detect a 20% difference in progression using 600 patients with initial EDSS of 4.0 per trial arm, or 400 patients with initial EDSS of 5.0 per arm. However, trials including patients with fixed EDSS of ≥6.0 will be underpowered even with large numbers or prolonged duration. CONCLUSIONS: Disability progression in PPMS is variable and influenced by age at onset. Although progression is more rapid, age-related disability milestones are identical to relapsing-onset disease. These data offer a contemporary paradigm for clinical trial design in progressive MS.