Quote:
Originally Posted by Natalie8
Can someone please explain why Biogen is now stating that the risk of PML is still 1:1000 from 24 to 36 months if only 13,000 people have taken the drug more than 24 months? I got the 13,000 number from an article dated Oct. 23. Haven't 18 of the PML cases been 24 months and over? Thanks!!!!
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Natalie,
Part of the problem lies in the fact that the PML case number is as of a relatively current date (Late Oct) and the 13,000 patient number is as of Sep 30th. More patients crossed the 24 month threshold in that time.
The other part of the problem is how ratios are calculated statistically with this small sample size. Because of this small sample size, there is potentially a large amount of variability in what the real answer will ultimately be. These calculation methods are universally accepted, hence the FDA's concurrence that the PML risk is similar to that seen during clinical trials.