Screening for possible failure of herpes simplex virus PCR in cerebrospinal fluid for the diagnosis of herpes simplex encephalitis.

The objectives of this study were to evaluate the reliability of herpes simplex virus (HSV) PCR testing in cerebrospinal fluid (CSF) for the detection of herpes simplex encephalitis. This was done by examining retrospectively the clinical follow-up of a large group of patients tested routinely by HSV-PCR. In addition, an attempt was made to assess the incidence of herpes simplex encephalitis in a central European population. CSF samples from 1,427 patients from all Vienna hospitals were submitted for HSV-PCR testing during a period of 4 years and 8 months. Herpes simplex encephalitis was detected by PCR in 12 cases and by serological methods in one additional patient. Retrospective analysis of the course of disease, which was possible in 799 PCR-negative patients, led to the identification of three additional cases in which herpes simplex encephalitis appears to have occurred despite negative PCR results. Failure of the PCR in these patients is most likely due to the time of obtaining CSF during the course of disease. A high specificity of the assay was demonstrated by the lack of false positive results in any of the 708 cases in which other causes for the neurological symptoms had been identified in the follow-up. The incidence of herpes simplex encephalitis in the population of Vienna was between 1 case/469,000–577,000 individuals/year. The highest annual incidence was detected in the age group between 3 months and 3 years, which, however, could not be confirmed statistically. J. Med. Virol. 64:531–536, 2001. © 2001 Wiley-Liss, Inc.