Canadian study shows no association between taking interferon beta and any reduction in progression to disability.
The study was not assessing or focusing on interferon beta’s ability to reduce relapses or prevent lesion formation.
Researchers at the University of British Columbia (UBC) used the British Columbia MS database (which has been in use since the 1980s) to assess the relationship between interferon beta use and disability progression in people with relapsing-remitting MS.
Researchers discovered that those who took the drug were no less likely to have long-term disability than those who didn't take the drug, when looking at a standard test, the Expanded Disability Status Scale (EDSS), to measure disability progression in MS.
The EDSS is a method of quantifying disability in MS and monitoring changes in the level of disability over time. The EDSS scale ranges from 0 to 10 in 0.5 unit increments that represent higher levels of disability. Scoring is based on an examination by a neurologist.
The researchers collected information on 868 people with MS who had taken interferon beta and 1,788 patients that had not, from 1985 to 2008. Those that had not taken interferon beta were split into two groups; 829 who were able eligible for the drug but did not receive it (untreated) and 959 who fit the criteria for the drug, but went untreated as it was before interferon beta therapies became available in 1995 in Canada (historically untreated).
The use of two control groups sought to eliminate the chance of bias based on those choosing not to receive therapy for reasons such as less severe disease, the researchers wrote.
Those who scored a 6 - meaning they needed a cane to walk 330 feet or 100 metres - were considered to have a disease that progressed.
- Out of the subjects who took interferon beta, 10.8 percent scored a 6.
- Out of the subjects who were untreated, only 5.3 percent
- 23.1 percent of the historically untreated group reached that same score. The historically untreated group had greater interval between assessments than the other two groups.
Previous studies have reportedly shown that interferon beta does help stall disease progression, but the researchers of this study said that the methodology was flawed through small sample sizes, poor follow-up or included patients who were too ill to start taking medication in the control group.
The senior author, Helen Tremlett, an associate professor of neurology at UBC, cautioned that the study does not show that interferon beta is ineffective. “These drugs were licensed because they reduce relapse and have a better outcome with lesions,” she said. “That has not changed.”
The authors acknowledge certain weaknesses of their study, in particular the problem that people who take no medicine are also likely to be among those who are the least ill and therefore least likely to become disabled in any case.
But after controlling for other factors, they could find no association between taking interferon beta and any reduction in progression to disability. Relapses and brain lesions do not, apparently, drive disability, Dr. Tremlett said.
The study was published on July 18 in The Journal of the American Medical Association.