I have just been told my JCV titre level is 0.63. What is the cut off level when on Tysabri?
The JC virus antibody index is reported as positive with values about 0.4, but there are no strict cut off values. By this I mean that an individual’s risk of PML depends significantly on their index value. Those with persistent index values below 0.6 have almost no risk of PML, those with persistent index values between 0.6 and 1.5 have an intermediate risk of PML and those with persistent index values > 1.5 have a high risk of PML with long term treatment.
Whether or not you chose to remain on Tysabri at any given index value depends on your response to prior treatments, your disease characteristics, your other medical problems and your aversion to risk.
Revere (Rip) Kinkel MD
Director of the Multiple Sclerosis Program
Professor of Clinical Neurosciences
University of California San Diego