The investigators’ data extend earlier paired, longitudinal studies in various countries of patients treated with natalizumab who had similarly high rates of conversion and a rise in titers, said Adil Javed, MD, PhD, Associate Professor of Neurology, and Anthony T. Reder, MD, Professor of Neurology, both at the University of Chicago, in an accompanying editorial. Although the JCV index appears to be a valid serum marker of risk for PML, “risk is relative,” they said. “Despite a higher JCV replication state, an increase in JCV-antibody index does not necessarily mean that PML infection is imminent…. Schwab et al extend growing observations that JCV-antibody index values need to be monitored and that seroconversion or rising JCV-antibody titers alter the risk of PML in patients treated with natalizumab.”
—Erik Greb