Outcomes from the 16-year LTF
The 16-year LTF explored the relationship between drug exposure and long-term disability. Statistical methods to mitigate the potential biases of outcome-dependent exposure variation were used† .
The major factors predicting better clinical outcomes were:
- Low EDSS (<2) at study entry
- BETAFERON exposure: Relative to patients with low exposure, those with high BETAFERON exposure* had a 60-70% reduced risk of a “negative outcome” (see figure). A “negative outcome” was defined as reaching an EDSS of 6, progression to secondary progressive MS or becoming wheelchair bound
Safety and tolerability findings of the study reinforced the favorable safety profile of BETAFERON: No new or unexpected side effects were reported; flu-like symptoms were still present at a low level and injection site reactions continued to be reported .
Data from the 16-year LTF: Relative to patients with low exposure, those with high BETAFERON exposure* had a 60-70% reduced risk of a “negative outcome” 
*Median Medication Possession Ratio (MPR) of high exposure (71%) vs low exposure (0%).
†Recursive partitioning method was used.
EDSS: Expanded Disability Status Scale.