Tysabri's been REWORKED now so that there is only a 1 in 1000 chance of getting a serious viral infection of the brain. Ho ho ho.
But on another MS site, a poster who appeared to know a lot about statistics, stated that you simply could not take those numbers and come up with the conclusion that they did...especially when it came to real statistics. He stated that several variables would have to be factored into any probability number that accurately determined what the real risk would be. Since he did not have access to these variables it was impossible to determine.
I'm sure there are more complicated ways of calculating the risk, but the simple facts appear to be that 3 out of 3,000 on the trial got PML. The simple risk is 1 in 1,000.
msladyinca wrote:3 patients out of 3,000 in the trials contracted PML.
2 of the PML patients received Tysabri in combination with Avonex. Eliminate them from the risk ratio as Tysabri can only be prescribed as a monotherapy.
1 of the PML patients received Tysabri as a monotherapy, however...note: he was a Crohn's patient with a severely compromised immune system which included a past medical history of use with very strong immune suppressant medications for his CD such as azathioprine (Imuran).
Thus, the unjust 1:1000 risk ratio for PML when using Tysabri, and the risk factor is probably much lower than the 1:1000 due to: "Tysabri is indicated for use as a monotherapy, meaning it should not be used in combination with other immune system modifying drugs, and is for patients who have not responded adequately to, or cannot tolerate, other treatments for MS. "
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