Data Dictionary

Definite Case

Brain Biopsy or biopsy pathologic confirmation of JC virus (JCV) infection in astrocytes and oligodendrocytes by immunohistochemistry or in situ DNA hybridization

Clinical symptom presentation compatible with PML,
and

Brain magnetic resonance imaging (MRI) findings consistent with PML,
and

JCV DNA detected in cerebrospinal fluid by polymerase chain reaction (PCR) assay

Probable Case (2 of 3 must apply)

Clinical symptom presentation
Or

Brain MRI findings consistent with PML

JCV DNA detected in CSF by PCR assay

Possible Case

Some clinical symptom presentation
Or

Brain MRI findings consistent with PML,
Or

JCV DNA not detected in CSF assay/CSF not obtained
Or

No history of immune suppressed condition/taking therapies that may cause immune suppression

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