| Blood tests Blood tests are available to determine whether you have been infected by herpes simplex virus type 1 or 2. It can be difficult to interpret the results of these tests. The AHMF recommends that you consult a clinician experienced in the management of herpes simplex infections both before having the blood test and when you receive the result. Most Australian laboratories perform an Enzyme Immunoassay test, which does not distinguish between HSV-1 and HSV-2. In other words, this test will give a positive result if you have been infected with either of these viruses. People who have had cold sores previously will have a positive result for this test whether or not they have genital herpes. On the other hand, a negative result means that you have never had either genital herpes or cold sores. This might be useful information for people whose sexual partners are known to have genital herpes. A negative result confirms that there is a risk of contracting the infection from the partner. A positive result that you have already been infected by the herpes simplex virus (although it does not show which type) and there is less risk of contracting the infection from the partner. A second test, known as the Western Blot, not performed by most Australian laboratories, can distinguish between HSV-1 and HSV-2. This test may be useful in diagnosing genital herpes in people who have a previous history of oral cold sores. Again, the results are not always clear cut because HSV-1 can cause genital herpes as well as cold sores and HSV-2 can cause cold sores as well as genital herpes. The Western Blot test can also be used to determine if an outbreak of symptoms is due to long-standing or new infection with HSV-1 or HSV-2. It is important to bear in mind that if evidence of HSV-1 and/or HSV-2 is detected in the blood, it does not necessarily confirm that symptoms at a given time are due to an outbreak of genital herpes. This diagnosis is still best made on clinical grounds with confirmation by a swab test. However, if there are recurrent symptoms which suggest genital herpes but the virus has never been isolated from a swab, the blood test might be helpful in supporting the diagnosis. |
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