The John Cunningham virus (JCV) is a generally benign and asymptomatic polyomavirus. Due to an association of the anti-integrin agent natalizumab with progressive multifocal leukoencephalopathy (PML) in patients with multiple sclerosis (MS), a newly developed anti-JCV antibody assay has been implemented as a risk-stratification tool for natalizumab-treated patients with MS. This viewpoint offers insight and perspective regarding the potential unapproved use of the anti-JCV antibody assay in rheumatoid arthritis (RA) and examines how rheumatologists can best assist patients.
A primary literature search was conducted to identify articles on the number of cases of PML associated with natalizumab in patients with MS, the number of cases of PML associated with patients with rheumatic disease, PML incidence in the general population, serum-based assays to detect JCV exposure, and clinical PML presentation and treatment methods.
Risk of PML in patients with RA receiving biologics appears orders of magnitude lower than that expected in natalizumab-treated patients with MS (1 in 1000). If patients with RA are risk stratified assuming an anti-JCV antibody seropositivity of 60%, theoretically 23,400 anti-JCV antibody-positive patients would have to receive rituximab before potentially observing 1 PML case.
Data currently indicate that rheumatologists should not order the anti-JCV antibody assay for patients requiring biologics. Monitoring relevant symptoms indicative of emerging PML might provide greater value to patients, thus prompting interventional measures that could affect prognosis.