larryob98 wrote:I am a new member, but we need to decide in the next 24-48 hours whether Tysabri or Tecfidera is the preferred initial course of treatment for my daughter. After exhaustive research, we still have ambiguous and conflicting information on PML risk.
Apparently, the risk of PML for someone who tests negative for JCV antibodies is less than 1 in 11,000. The only way to interpret that statement, since you can't get PML without exposure to the JC Virus, is that in thee cases, the test results were a false negative (3% risk) , and that the patient has been exposed to the JC Virus at some point during the six month period prior to the false negative and for an additional period after the false negative until either the next JCV test or a PML diagnosis. so that the 1 in 11,000 risk is a combination of true negative and false negative patients. This risk apparently does not depend on how long one has been on Tysabri.
If, on the other hand, the patient tests positive for the JC Virus, the risk of PML does depend on how long one has been (past tense) on Tysabri, and for those on Tysabri less than 2 years, that risk is 1 in 1786, assuming no additional risk factors such as the prior use of other immunosuppressants (overcomingmultiplesclerosis.com)
This suggests that at the point at which a patient first tests positive for the JC Virus, past Tysabri use is an issue (i.e., it's not just patients who test positive and continue with Tysabri, but also patients who have never tested positive before the first positive result.
So if you are on Tysabri for up to two years, and you have your first positive JCV result, you already have a 1 in 1786 risk of PML
This, of course, in inconsistent with the risk of patients who test negative not having an increased risk based on how long they have already been on the drug. Since every web page and every medical journal article is written by Biogen Idec, tbere is no variation in the endless repitition of ambiguous language on this point. Any clarification, especially from a published source,would be most welcome.
With more than 115,000 patients globally treated with natalizumab for longer periods of time, that estimate number of PML cases is 1 per 330. In patients who test positive for antibodies to JCV, have a clinical history of immune suppressive treatment before natalizumab, and have received more than 24 doses, the number of PML cases is 1 per 90.
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