I am a nurse, and as part of my job, I collect specimens for HIV testing. However, I am confused about how HIV can be tested in urine and saliva if it cannot be spread via these two fluids. Can you please explain how the lab can test urine and saliva with accuracy?

M.

There are several points to be made about your question. First, it is true that urine and saliva are very unlikely sources for infection with HIV (human immunodeficiency virus, the microbe that causes AIDS). Urine, for example, is not considered to be infectious at all. HIV can be found in small amounts in saliva, but so little virus is present in saliva that a human bite is not considered a significant risk for transmitting HIV.

Nevertheless, urine and saliva can be used to test people for HIV infection, because both fluids contain significant amounts of antibodies against HIV. Antibodies are proteins a person's immune system creates to fight an infection.

The standard HIV tests detect antibodies against HIV in the blood. These tests are highly accurate and are considered the best for diagnosing HIV infection. It is now possible to detect antibodies in urine and saliva using virtually the same methods as the standard blood tests.

One advantage of urine and saliva testing is that the patient does not need to have blood drawn with a needle. This makes it easier and less painful to obtain a sample, particularly with very young children. In addition, this method of collection is safer for the health-care worker, because there is very little risk that the worker will be exposed to the virus, something that can occur if he or she is accidentally stuck with the same needle used to draw the patient's blood.

As far as accuracy goes, the urine and saliva tests are excellent. They are essentially as accurate as blood tests if the result is negative. If the result is positive, experts recommend that the result be confirmed with a standard blood test.