(6 Nov 2001)

Genital herpes is caused by one of two herpes simplex viruses (HSV-1 or HSV-2), both of which are passed on from person-to-person through direct intimate contact.

Around 80% of all cases of genital herpes still remain undetected and undiagnosed. Studies have shown that a high percentage of people become infected from an undiagnosed partner, so improving diagnosis is therefore key in helping to reduce the spread of infection. Genital herpes often goes undiagnosed because of the wide range of symptoms associated with the infection, or because in some cases, there is a total absence of any visible signs or symptoms. Poor diagnosis can also be linked to a fear or embarrassment associated with having a sexually transmitted infection, which prevents some people from seeking medical help.

HSV-2 is the most common cause of genital herpes, whereas HSV-1 is the most common cause of facial herpes or cold sores, however cross infection can frequently occur. Being able to establish, through a diagnostic test, which virus is the cause of the infection is important because it will influence how the condition is managed. HSV-2 infection is more likely to recur in the genital area and therefore the patient may benefit from more frequent or continuous therapy known as suppressive therapy.

An accurate diagnosis can help people who are infected take control of their health and benefit from treatments that may reduce their symptoms and their frequency of infection. A diagnosis also means those infected can reduce the risks of passing the virus onto their partners.

Key considerations for any form of diagnosis

• Speed - so a result can be given as quickly as possible
• Accuracy - every patient has a right to an accurate diagnosis
• Type-specific - ensuring the physician knows whether infection is caused by HSV-1 or HSV-2 and can therefore advise on the most effective treatment

How to diagnose genital herpes

A physician may use one or more of the following most commonly used methods to diagnose genital herpes, depending on each situation.

A physical examination - Classic signs of HSV infection such as fluid filled blisters or lesions are relatively easy to identify, however a physical examination is not always reliable because of the wide range of symptoms associated with the infection. Some of the signs of genital herpes can be confused with other conditions such as candidiasis (thrush), urinary tract infections or skin conditions affecting the genital area.

Virus culture detection tests - This test involves using a moist cotton wool swab to collect a sample of virus from the infected area. The sample is then tested, usually in a laboratory. The problem with this detection method is that the person must have a ‘live’ or ‘active’ infection at the time of the swab test. If any blisters, lesions or ulcers have begun to heal the test may not give an accurate result. However, when active lesions are present, this method is seen as the gold standard diagnostic test.

Serology (blood) tests - When someone becomes infected with HSV the body will produce antibodies designed to fight the virus. These antibodies are specific to each virus and remain permanently in the bloodstream. A blood test for a herpes simplex virus can tell if someone has been infected at some time during their life. However it cannot indicate when or where on the body the initial infection took place, for example whether around the genital or facial area. Also antibodies take time to develop following initial exposure to a virus and for HSV-1 and 2 this is normally up to 3 months. Therefore if a blood test is carried out too soon after infection first takes place, it may give a false negative result, that is, come back negative, when in fact the person has been infected, but only recently.

The older blood tests could not reliably tell the difference between HSV-1 and HSV-2 antibodies, but there are new commercially available tests that have recently been developed bringing new options for diagnosing HSV.

New herpes diagnostic tests - Type-specific blood tests are becoming more widely available. They can help to confirm a visual diagnosis of herpes and identify unrecognised cases where symptoms are either absent or difficult to define.

This year has seen the launch of the following new tests, although they are not yet available in every country.

The HerpeSelect™ type-specific HSV antibody detection tests produced by Focus Technologies. These test kits work by taking a blood sample from the patient's arm and then sending the sample to a laboratory for analysis. They can effectively distinguish between HSV-1 and HSV-2.

The POCkit® HSV-2 Rapid Test has been developed by Diagnology. It is a point-of-care test, which means it can be carried out by the physician within their surgery or clinic without the need for a laboratory analysis. It uses a small sample of blood taken by pricking the fingertip and, according to Diagnology, results can be read in 6 minutes. This test can only detect HSV-2 and therefore will not rule out the possibility of a person having genital herpes caused by HSV-1.

Everyone has a right to an accurate diagnosis, appropriate treatment and up-to-date information. For more information about these new tests please see www.focusanswers.com and www.pockit.com.