CD4 and progressive multifocal leukoencephalopathy: In the cART era, a significant reduction in the diagnostic positive detection rate and in the predictive value of the negative test were observed.33The immune reconstitution, represented by CD4 count above 100 cells/μl was demonstrated to be an independent predictor of failure to detect JCV DNA in the CSF of PML patients.33In this context, monitoring the quantitative CSF JCV-PCR testing over time could be an indicator of PML-IRIS.