Article Text

Download PDFPDF
Short report
Performance of PML diagnostic criteria in natalizumab-associated PML: data from the Dutch-Belgian cohort


Objective To test the current progressive multifocal leukoencephalopathy (PML) diagnostic criteria by applying them to patients previously diagnosed with natalizumab (NTZ)-associated PML in a real-world clinical setting.

Methods Patients from the Dutch-Belgian NTZ-PML cohort (n=28) were reviewed at the time of first diagnostic work-up and during follow-up, using the PML diagnostic criteria as proposed in a consensus statement from the American Academy of Neurology.

Results At first diagnostic work-up, 18 patients (64.3%) met the criteria for high diagnostic certainty for PML (‘definite PML’ or ‘probable PML’). During follow-up, this increased to 20 patients (71.4%) as JC virus DNA was detected in cerebrospinal fluid of two additional patients. Nonetheless, 28.6% of patients were still classified as ‘possible PML’ or ‘not PML’ (6 (21.5%) and 2 (7.1%) patients, respectively) despite a very high suspicion for PML based on lesion evolution and signs of PML-immune reconstitution inflammatory syndrome on MRI, and development of compatible symptoms.

Conclusions The current case definition of PML has low sensitivity for diagnosis of NTZ-PML in a real-world clinical setting in which MRI is frequently used for PML screening. This may delay diagnosis and appropriate management of PML, and may complicate a valid estimation of PML incidence during NTZ therapy.

  • progressive multifocal leukoencephalopathy
  • diagnosis
  • JC virus
  • natalizumab
  • multiple sclerosis

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.