after doing MRI in north york general in toronto my doctor (Lavitan) told me that I should do an antibody blood test in st. Michael hospital with DR.Daniel Selchen. I am waiting for the call to go for the test. I hope this is Negative but I am goring to contribute to this blog for those with same situation may God help us all

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Background JC virus (JCV) seropositivity is a risk factor for progressive multifocal leukoencephalopathy (PML) in patients on natalizumab. Accordingly, the JCV serological antibody test is of paramount importance in determining disease risk. Methods We tested the accuracy of the JCV serum antibody test by comparing the results of JCV serology to JC viruria and viremia in 67 patients enrolled in a single-center, retrospective cohort study. Bodily fluids (urine and blood) were assessed for JCV DNA by real time quantitative polymerase chain reaction 6 to 47 months earlier (mean 26.1 months) before JCV antibody testing. In 10 individuals, blood and urine samples were obtained on two separate occasions at 6 month intervals. Results Forty (59.7%) of the 67 patients were JCV seropositive. Of 27 JCV seronegative patients, 10 (37%) had JC viruria. Urine JCV DNA copy numbers were significantly higher in the seropositive group (mean log copy number: 5.93; range 1.85 – 9.21) than the seronegative group (mean log copy number: 2.41; range 1.85 – 5.43) (p=0.0026). Considering all body fluid test results, 50 (74.6%) of the 67 patients were previously infected with JCV. Conclusions The false negative rate of the JCV serology in this study was 37%; therefore, JCV serostatus does not appear to identify all patients infected with JCV. Thus, a negative JCV antibody result should not be conflated with absence of JCV infection. This discordance may be important in understanding JCV biology, risk for PML and PML pathogenesis. PMID:23526716