PCR stands for polymerase chain reaction. It is a method in which HIV RNA is copied millions of times to a measurable amount.
The PCR test is more modern and more complicated than antibody detection tests. HIV's genetic information is in the form of RNA, so first it needs to be converted into DNA for PCR to be performed. A piece of corresponding DNA is attached to the single strand HIV RNA. The enzyme polymerase completes the RNA into DNA, which is reverse transcription. Once this happens, the DNA is split into two strands by heating. The corresponding DNA primer comes again and polymerase makes an additional copy. This process is repeated until the HIV can be detected.
For clarification and more information see http://www.roche-hiv.com/Newsandfeatures/animations/PCRtutorial.cfm?link=PCRtutorial .
Sources:
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“AIDS.” Encyclopedia Britannica. 2004. Encyclopedia Britannica Online. 4 Jan. 2004. <http://search.eb.com/eb/article?Eu=4225>.
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James, John S.. "PCR Test Now Available." AIDS Treatment News 15 July 1988. 24 Jan. 2004 <http://www.aegis.com/pubs/atn/1988/ATN06002.html>.
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"Measuring the Virus." April 1995. AIDS Treatment Data Network. 10 Feb. 2004 <http://www.aegis.com/pubs/atdn/1995/ATR01805.html>.
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“PCR Tutorial." 2004. F. Hoffmann La Roche Ltd. 24 Jan. 2004 <http://www.roche-hiv.com/Newsandfeatures/animations/PCRtutorial.cfm?link=PCRtutorial>.
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"Viral Load Tests." The Simple Facts Project . 2002. AIDS Treatment Data Network. 16 Jan. 2004. <http://www.aegis.com/factshts/network/simple/viral.html>.