The value of anti-JCV antibody index assessment in multiple sclerosis patients treated with natalizumab with respect to demographic, clinical and radiological findings

Abstract Background Natalizumab-related progressive multifocal leukoencephalopathy (PML) is associated with the presence of anti-John Cunningham virus (JCV) antibodies. The aim of this investigation was to evaluate the long-term stability of anti-JCV antibody serum levels and their relation to various demographic, clinical and radiological characteristics in patients suffering from multiple sclerosis (MS). Methods Seventy-eight relapsing-remitting MS patients treated with natalizumab and evaluated for the presence of serum anti-JCV antibodies over a time period of 1–6 years (3–11 samples) were included in the study. Anti-JCV antibody levels and their changes were correlated with various demographic, clinical and radiological findings. Results Median follow-up time was 43.5 months, with a median of 5.3 samples available per patient. At baseline, 46 (59%) of the patients were seropositive. During follow-up, anti-JCV antibody status changed from negative to positive or vice versa in 23% of patients. Baseline anti-JCV antibody index correlated positively with age ( p  = 0.03). Patients with stable positive anti-JCV antibody index had more T2 hyperintensities (20.2 vs. 13.1; p vs . 40.3 years; p n  = 13) was 33 months. Annual seroconversion rate of anti-JCV antibody status was 6.5%. A baseline anti-JCV antibody index of >0.90 ( n  = 33) predicted stable seropositivity (100%), while baseline anti-JCV antibody index Conclusions A positive baseline anti-JCV antibody index of >0.90 predicts stable positive JCV serostatus, in contrast with a baseline anti-JCV antibody index of