cyosta@decwrl.dec.com ( Yossie Silverman) (11/08/89)
What is the polymerase chain reaction test? The polymerase chain reaction is a new tool for the detection of viral DNA. the reaction amplifies extremely small amounts of DNA to detectable levels. Thus, it forms the basis of a very sensitive test which will detect a single molecule of viral DNA among the DNA of a host cell. The two strands of DNA are first separated by heating and then a heat-stable polymerase enzyme (derived from thermophilic bac teria found in geysers) zips along the starands to produce two double-stranded molecules. By repeating this process, multiple copies of the original molecule of DNA can be made. The test was developed in the USA, and has only recently become available to researchers in other countries. Studies in which the test has been used must be viewed with caution at present because its extreme sensitivity means that it is vulnerable to contamination, which could cause a high rate of false-positive results. The test has already produced some controversial findings. A useful application of the test may be the diagnosis of HIV infection in an individual who has a negative HIV antibody test. False-negative HIV antibody tests can occur through laboratory error or because the antibody has not yet developed. If the polymerase chain reaction test becomes widely available, it could become the next diagnostic step after a negative antibody test in an individual who has high risk of becoming infected with HIV. For example, HIV virus has been detected with the polymerase chain reaction test in several individuals many months before conventional HIV tests gave any indication of infection: in one individual the virus appeared to be present 42 months before the antibody tst became positive. If this finding is confirmed there are important implications for the screening of blood donations. The test may enable true HIV infection in neonates to be distinguished from HIV-positivity due to the transfer of antibody from the mother. Use of the test has also suggested that in the rare cases of an HIV-positive person becoming HIV-negative, the virus has not been eliminated but is probably present in a latent form. (c)Medicine International, 1988 -- Yossie Silverman What did the Caspian sea? National Semiconductor Ltd. (Israel) cyosta%taux01@nsc.nsc.COM or RPR1YOS@TECHNION.BITNET NSA LSD FBI KGB PCP CIA MOSAD NUCLEAR MI5 SPY ASSASSINATE SDI -- OOLCAY ITAY