The FDA has approved a labeling change for Tysabri (natalizumab; Biogen Idec) that identifies anti-JCV antibody status as a risk factor for progressive multifocal leukoencephalopathy (PML) in patients receiving Tysabri for the treatment of multiple sclerosis (MS) or Crohn’s disease. The labeling update was based on analysis of data from Biogen Idec’s and Elan’s quantitative risk-stratification algorithm that showed that patients who were anti-JCV antibody positive were at an increased risk for developing PML with varying degrees of risk depending on prior immunosuppressant use and Tysabri treatment duration.

Focus Diagnostic’s Stratify JCV Antibody ELISA test has been approved by the FDA to be used in combination with other clinical data to help providers determine antibody-JCV status and the risk for developing PML in MS and Crohn’s disease patients.

For more information, call Biogen Idec at (800) 456-2255 or visit or