An Improved PCR Assay of Viral DNA in Cerebrospinal Fluid from Patients with Herpes Simplex Virus Type‐1 Encephalitis

: Several investigators have attempted to establish a simple, sensitive and quantitative method for a PCR assay of viral DNA in the cerebrospinal fluid (CSF). However, the rate of a positive DNA test differs between laboratories using the same CSF samples from patients with herpes simplex virus type-1 (HSV-1) encephalitis because of differences in sensitivity of the detection. In the present study, we compared the sensitivity and quantity of nested PCR amplification from the pretreated CSF (nested PCR) with those of direct PCR that was performed by direct PCR amplification of the small amounts of CSF to the PCR “cocktail.” We studied the advantages of the two different methods, “the direct and nested PCR,” and established a two-step method as an improved PCR assay. HSV-1 DNA from the CSF samples obtained within 4 weeks after onset was detected in all seven cases.