Diagnosis

• The Importance of Diagnosis :
  There is no cure for HSV infections. Once a primary infection of a herpes virus establishes latency, it will persist in the host's cells for life. Antiviral medication is available to treat most herpes virus infections and has been shown to decrease symptomatic recurrences of genital herpes, including the frequency of viral shedding and the transmission of the virus to sexual partners. All patients with suspected genital herpes simplex infection requiring therapy should have confirmation of infection. The Pharmaceutical Benefits Scheme (PBS) requires doctors to provide proof of microbiological confirmation of the diagnosis whenever they prescribe antiviral medication .It is important to note that confirmation of the diagnosis should not delay appropriate therapy.

• Methods of Diagnosis :
  A)Virus Isolation

Figure : Vesicles in a genital herpes lesion.
AHMF: The Diagnosis of Herpes Simplex Virus Infections.

* Virus isolation is most sensitive when lesions are fresh and moist.
* Taking a sample for culture requires breaking a fresh lesion and collecting vesicle fluid and cells rubbed from the base of a lesion.
* It using a rayon-tipped plastic swab to transport the sample to an appropriate viral transport medium.
* Virus isolation as a method of diagnosing herpes infections requires optimal collection and transport conditions, and some pathology laboratories no longer routinely use this method.
* Distinguish between HSV-1 and HSV-2 infection and swabs can be taken from mucocutaneous sites such as endocervical swabs, anogenital swabs, throat and conjunctival swabs. A negative test result does not exclude infection.



B)Direct Antigen Detection



Figure: Immunofluorescence on cell culture.
AHMF: The Diagnosis of Herpes Simplex Virus Infections.


* Direct Antigen detection sample collection requires vesicle fluid and cells rubbed from the base of a lesion.
* It using a rayon-tipped plastic swab.
* Tissue or material from the eye or CFS may also be submitted for rapid antigen detection if herpes encephalitis or ocular infection is suspected.
* This is then transported in an appropriate viral transport medium.
* Direct Antigen detection is a rapid, type specific and sensitive method for detecting HSV.
* Procedure involves a direct immunofluorescence using fluorescein- labelled monoclonal antibodies specific for HSV antigens.
* It has high sensitivity, when vesicles are present, however, sensitivity will fall as lesions heal.
* A negative test result does not exclude infection.



C)PCR



Figure: PCR Roche LightCycler 2.0, Image supplied by Roche Diagnostics Australia Pty Ltd.
AHMF: The Diagnosis of Herpes Simplex Virus Infections.


* Genomic detection by polymerase chain reaction (PCR).
* It is highly sensitive, fully automated and more rapid than viral culture or direct antigen detection.
* PCR allows simultaneous detection and differentiation of HSV-1 and HSV-2.
* It is more sensitive than other detection methods late in infection when the lesions have begun to crust.
* The most commonly used commercial kit is Roche LightCycler HSV 1/2 Detection Kit but the Artus HSV-1/2 PCR kit is also available. A negative test result does not exclude infection.



D)Type Specific Serology
* A blood sample taken for detection of antibodies to HSV.
* HSV antibody testing can reveal acute infection or previous exposure.
* HSV type-specific antibody testing is available using Western blot or enzyme immunoassay.
* Some of the tests only detect HSV-2 infections; others are able to detect both HSV-2 and HSV-1 infections.
* Currently the HSV-1 tests are specific, but have unacceptably low sensitivity.
* HSV-2 specific tests appear to be more sensitive but one widely used test has been shown to have a relatively high rate of false positives.
* Type-specific serology may be useful where culture and PCR are repeatedly negative, to identify infected patients and to help them recognise symptoms and to reduce the chance of transmission to sexual partners.
* HSV type-specific IgM can be detected in acute infection, usually within a few days of clinical lesions, but may take up to 3 weeks to appear.
* Specific IgM response may also appear in severe clinical recurrences. Individual episodes of recurrent genital herpes cannot be reliably diagnosed by serological testing.

References :
1. BMJ Publishing, 2003: Psychosocial impact of serological diagnosis of herpes simplex virus type 2: a qualitative assessment. Internet: http://sti.bmj.com/cgi/content/abstract/79/4/280
2. International Herpes Alliance: Diagnosis and Diagnostics. Internet : http://www.herpesalliance.org/diagnostics.htm
3. AHMF: The Diagnosis of Herpes Simplex Virus Infections. Internet : http://www.ahmf.com.au/health_professionals/guidelines/diagnosis_of_hsv.htm
4. SpringerLink: New strategies for the diagnosis, treatment, and prevention of herpes simplex in contact sports. Internet: http://www.springerlink.com/content/4r51n36q01215134/

Comments and inquiries are always welcome.

Prepared by Teh Yong Jiann 1061105152