Reverse transcriptase
PCR is frequently used to for rapid identification of specific DNA viruses from the CSF, while Reverse transcriptase PCR is commonly used to identify RNA viruses in the CSF. The accuracy of this diagnostic tool is limited by the amount of the virus present in the CSF. Viral replication tends to peak early and then decline to undetectable levels in CNS infection. Within the first 5 days of symptom onset, before the decline of viral replication, PCR assays have a higher incidence of detecting CNS infection.