I am on infusion #81 of Tysabri. I am JCV Positive and have always had a low index level. I just had my highest index level come back at .67, I know this is still relatively low but I am a worrier and have had prior IS treatment with Novantrone and Methotrexate and I know that increases my risk of PML. I can't find any answers about how many people have developed PML at these lower index levels, do you have any information about that? Is there any information about the LOWEST index rate in someone who has gotten PML?
Risk of PML in people who have previously been treated with immunosuppressants, especially Novantrone, is determined solely by the presence of absence of JCV antibodies, not the index value. Your risk of PML would be consider about 1 in 100 or even slightly greater than this risk, because even though you are low titer positive, you were previously treated with Novantrone. Many individuals in your circumstance go on an alternate dosing schedule (infusions every 2 months) and get brief MRI scans every 4 months to detect early PML if this should happen. This has been an effective way to decrease the risk of PML further although results on this protocol are only preliminary. If you do not go on an alternate dosing schedule it may be wise to stop Tysabri and start another highly active therapy immediately (usually Rituximab or Gilenya), but as always, discuss this information with your physician.
Revere (Rip) Kinkel MD
Director of the Multiple Sclerosis Program
Professor of Clinical Neurosciences
University of California San Diego
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