A patient who tests negative for JC virus antibodies and who uses Tysabri may feel like jumping for joy at this negative test result. However, the the FDA stresses that “patients who test negative for anti-JCV antibodies are still at risk for the development of PML due to the potential for a new JCV infection or a false negative test result.” It seems obvious that doctors should consider testing patients prior to beginning treatment or during treatment if the antibody status is unknown. Patients should also consider periodic re-testing for those who previously tested negative for the anti-JCV antibody as a person might later become exposed to the virus.
For the past couple of years, discussions of Tysabri, PML, and the JC virus have been common in the MS community. Medical professionals have known that a reactivation of the JC virus is responsible for the development of PML in some patients. But until now there had not been a commercially-available laboratory test which would reliably test for the presence of anti-JC virus antibodies in a person’s blood. Now available through Quest Diagnostics, the Stratify JCV Antibody ELISA test is manufactured by Focus Diagnostics of Cypress, Calif. The test is for professional use and by prescription only and is to be performed only at Focus Diagnostics’ Reference Laboratory.
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The JC Virus Antibody Test Goes Public