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MS-related disability may be decreasing


 

EXPERT ANALYSIS FROM ECTRIMS 2019

The long-term prognosis of multiple sclerosis has improved markedly around the world,, according to an overview provided at the annual congress of the European Committee for Treatment and Research in Multiple Sclerosis. Data consistently indicate that the time that elapses before a patient requires a cane for ambulation has increased, and survival has likewise improved. “Some of the improvement can be attributed confidently to treatment effect,” said Ilya Kister, MD, associate professor of neurology at NYU Langone Health in New York. “We hope to see an even greater change with newer therapies.”

Dr. Ilya Kister, associate professor of neurology at NYU Langone Health in New York

Dr. Ilya Kister

At the same time, neurologists appear to be diagnosing more cases of MS than they previously did, said Dr. Kister, which suggests that neurologists probably are diagnosing milder cases. The overall societal burden of MS remains high.

The relative prevalence of mild disability has increased

About 25 years have elapsed since the first disease-modifying treatment (DMT) for MS became available, and treatment has become widespread during that time. Dr. Kister and colleagues sought to determine whether the current clinical population of patients with MS, who for the most part receive DMTs, has less disability than do untreated patients or patients from natural history studies do. They identified the MS Severity Score (MSSS) as a measure with which to compare populations. The MSSS assigns a patient a ranking according to his or her level of disability, using a reference population of patients with the same disease duration for comparison. “MSSS can be conceptualized as rate of disability accumulation,” said Dr. Kister. “Lower MSSS corresponds to relatively slower disability accumulation, and higher MSSS to higher disability accumulation.”

The MSSS was developed using the Expanded Disability Status Scale (EDSS) score as a measure of disability. Because many neurologists do not routinely obtain EDSS scores for their patients, Dr. Kister and colleagues used the Patient-Determined Disease Steps (PDDS) to measure disability. As its name implies, the PDDS is a patient-reported outcome measure that mainly measures ambulation. It correlates strongly with EDSS, said Dr. Kister. He and colleagues used the PDDS to develop a reference table of MS disability, which they called the Patient-Derived MSSS.

The investigators examined a large sample of patients at NYU MS Center and Barnabas MS Center in Livingston, N.J. They grouped patients into sextiles according to their Patient-Derived MSSS. Dr. Kister and colleagues found that, rather than arriving at sextiles that contained equal numbers of patients, as would be expected if disability were distributed as in the reference population, they had significantly more patients in the two lowest sextiles and significantly fewer patients in the two highest sextiles. “This [result] suggests that the disability curve has indeed shifted toward the more benign end of the spectrum in the contemporary clinic population,” said Dr. Kister.

Other researchers have observed a similar phenomenon. George et al. published the results of a large, international collaboration in Neurology Genetics in 2016. After examining more than 7,000 patients, the investigators noted a similar overrepresentation of patients with milder severity scores and underrepresentation of patients with higher severity scores. These results support the hypothesis of a shift toward milder disability, said Dr. Kister.

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