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Progressive multifocal leukoencephalopathy (PML) is a severe adverse event in patients with multiple sclerosis (MS) treated with natalizumab. Brain MRI can detect small PML lesions at an early disease stage.1 Therefore, MRI screening is recommended for patients at high risk of developing PML.2 Diagnosis of PML is confirmed by brain biopsy or detection of JC virus (JCV) DNA from cerebrospinal fluid (CSF).3 However, in spite of using ultrasensitive quantitative PCR (qPCR) protocols, patients with PML can be JCV DNA negative in CSF, hampering the diagnosis. Recently, we demonstrated that the detection of intrathecally produced anti-JCV IgG antibodies is highly specific for diagnosis of PML, making the so-called CSF JCV antibody index (AIJCV) a candidate tool for earlier diagnosing of PML in a proportion of natalizumab-associated PML patients.4
The aim of this study was to assess the value of the AIJCV in a case series of natalizumab-treated patients with MS undergoing enhanced MRI pharmacovigilance for PML.
Patients and methods
Natalizumab-treated MS patients screened for PML using MRI (T2, fluid attenuation inversion recovery (FLAIR), diffusion weighted imaging) at the VU University Medical Center Amsterdam, and referrals, were included in the study. Patients with MRI suspicion of PML and a serum/CSF pair for assessment of the AIJCV at time of first MRI suspicion of PML were eligible. JCV DNA by qPCR and the AIJCV in CSF were determined at the Institute of Virology, University of Düsseldorf, Germany, and methods and cut-points (1.5 for the AIJCV) were applied as recently described.4 The study was approved by the local institutional review board, and written informed consent was obtained from all participants.
Basic characteristics of the patients included are provided in the online supplementary table. Median age was 46 years, and five of eight patients (63%) were female. Six …
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