Information for Neurologists on PCR FOR HSV
Herpes Simplex Virus (HSV) is the most common cause of sporadic focal central nervous system (CNS) disease. Without prompt antiviral therapy with acyclovir, the mortality rate may be as high as 70%. HSV is the most frequently detected virus in the clinical virology laboratory; however, the virus is rarely recovered from cerebrospinal fluid (CSF) except from infants with neonatal CNS disease or from other patients with meningitis. In 1990, Rowley et. al. demonstrated detection of specific HSV gene sequences by PCR in CSF samples from four patients with brain tissue-proven HSV encephalitis.

Before the introduction of molecular techniques, laboratory diagnosis of viral infections of the central nervous system (CNS) relied on virus isolation in cell culture, detection of specific antibody production in cerebrospinal fluid (CSF) or serum or antigen detection in brain biopsy in encephalitis caused by Herpes Simplex Virus (HSV). Deficiencies in traditional laboratory techniques with regard to the diagnosis of viral CNS infection have meant that in many patients a clinical diagnosis of viral meningitis is made without supportive laboratory evidence of a viral etiology.

Diagnostics Assays
Viral Antigen

Detection in tissue from brain biopsy specimens is highly invasive and the sensitivity of this assay in CSF is very low.

Although isolation of the virus from brain biopsy tissue is considered the definitive laboratory diagnostic test for CNS infection due to HSV, collection of this specimen for microbial diagnosis is very uncommon in routine medical practice because of the time taken to produce a characteristic cytopathic effect in cell culture.

Immunologic Analyses

Antibody testing of serum specimens may be useful in the acute-phase setting, but there is an age-dependent increase in baseline sero-prevalence. This greatly diminishes the diagnostic value of sero-conversion as an indicator of acute infection.

Polymerase Chain Reaction (PCR)
Over the past several years, the laboratory diagnosis of CNS disease due to HSV has been facilitated greatly by PCR. The assay is rapid, sensitive, and specific enough to be used as a frontline test for the detection of HSV DNA, thus avoiding invasive and expensive brain biopsy specimen procedures, which have been previously used as a benchmark for the laboratory diagnosis of HSV encephalitis. In addition, HSV DNA can be detected as early as 1 day after onset of clinical disease. The persistence of target DNA for an average of 14 days (range of 1 to 30 days) in CSF enhances the diagnostic sensitivity of this assay compared to that of HSV antigen or cell culture recovery of the virus, which have a narrower diagnostic window (8-10 days). Thus the rapidity, sensitivity (up to 98%), specificity (100%) and non-invasiveness of this test make it an ideal test for the diagnosis of HSV infection.

Information on Collection of Sample for Neurologists

Clinical Indication	Specimen	Volume	Collection	Storage	Transportation
Meningitis	CSF	1-2 ml	Sterile Container	*At 40C	**In Gel Pack Box
Encephalitis	CSF	1-2 ml	Sterile Container	*At 40C	**In Gel Pack Box

*	In middle shelf of refrigerator
**	Special transportation box available from Auroprobe Laboratories

References
	Cassinoti P, Meitz H, Seigl G. 1996. Suitability and clinical application of a multiplex nested PCR assay for the diagnosis of Herpes Simplex virus infectious. Journal of Medical Virology 50: 75-81
	Mitchell PS, Espy MJ, Smith TF, Toa DR, Rys PN, Berbari EF. 1997. Laboratory diagnosis of central nervous System infections with Herpes Simplex Virus by PCR performed with cerebrospinal fluid specimens. Journal of Clinical Microbiology 35 : 2873-2877
	Tang YW, Mitchell S, Espy MJ,Smith TF, Persing TH. 1999. Molecular diagnosis of herpes simplex virus infections in the central nervous system. J Clin Microbiol 37: 2127-2136