Lower risk of disability progression in primary progressive versus progressive-relapsing MS
medwireNews: Superimposed relapses are associated with a lower risk of confirmed disability progression among individuals with progressive-onset multiple sclerosis (MS), suggest the results of an observational cohort study published in JAMA Neurology.
Compared with 866 participants with primary progressive MS (PPMS), the 553 individuals with the disease subset of progressive-relapsing MS (PRMS) had a significant 17% lower likelihood of confirmed disability progression.
Further analysis showed that disease-modifying therapy (DMT) reduces the likelihood of disability progression in individuals with PRMS, with a significant 4% relative decrease in the risk of confirmed disability progression events for each 10% increase in DMT persistence. However, no such association was seen in the PPMS group.
And while previous studies have reported no difference in the age at onset between individuals with and without relapse, Tomas Kalincik (Royal Melbourne Hospital, Victoria, Australia) and colleagues found that patients with PRMS tended to be younger at disease onset than those with PPMS, with a mean age of 39 versus 43 years.
The data for this study were obtained from the MSBase registry, which holds information on 44,449 individuals with MS from 36 countries. Disability was measured using the Expanded Disability Status Scale (EDSS), and relapse was defined as new symptoms or the exacerbation of existing symptoms for at least 24 hours in the absence of another illness or fever, and at least 30 days after a previous relapse. Confirmed disability progression was defined as a 0.5- to 1.5-step increase in the EDSS score, depending on the baseline score.
Sensitivity analyses indicated that the association of DMT with disability progression is the result of controlling the worsening of relapse-related disability, reflecting differences in the underlying natural history of PRMS and PPMS, the researchers say.
They comment: “These findings provide further evidence for a progressive-onset MS phenotype with acute episodic inflammatory changes, thereby identifying patients who may respond to existing immunotherapies.
“Relapse, as a clinical correlate of acute episodic inflammation in progressive-onset MS, therefore constitutes a prognostic marker and a treatment target.”
By Catherine Booth
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