HIV test and other blood tests with PCR?

Could anyone help me by explaining what exactly a Polymerase Chain Reaction is or a "PCR test?" Like what is it used for? I heard it is used to find HIV, but what else?

Also do like all hospitals have them? How does it work? How much do they cost because I hear that they are expensive.

Thanks

How It Works

The PCR (polymerase chain reaction) is a major scientific advance which will be an important tool for many kinds of basic research, and for diagnosis of other diseases as well as AIDS.

The PCR test works by taking advantage of the fact that DNA can make a copy of itself, as it does during normal cell
division. The sample being tested is treated in such a way that each piece of the DNA being tested for will double into
two pieces. The treatment is repeated, and the two pieces become four, then eight, then 16, etc. After 20 or more repetitions, the DNA (if any) will have multiplied more than a million times, and then it can be detected by ordinary
biochemical tests.

The PCR can detect HIV infection even if it is completely latent, in the DNA of macrophages or other cells, not causing
the replication of virus or the production of antibodies.

Persons who are antibody positive would presumably always test positive with the PCR. Those who are antibody negative despite high risk of exposure to HIV could use the PCR for reassurance if they are negative, or to start early infection control, periodic blood work, or early treatment if they test positive.


The PCR is now available with a physician's prescription everywhere except New York State, which requires special licensing the companies have not yet obtained. The cost for the test itself is $145., and it takes about five days to get the results.