Clinical Applications of the Polymerase Chain Reaction

Abstract

The polymerase chain reaction (PCR) is a technique that allows a million-fold, or greater, amplification of defined regions of DNA or RNA. It is potentially capable of detecting a single copy of a gene, present only once in 105 eukaryotic cells. This remarkable level of sensitivity has allowed the development of many diagnostic assays for human pathogens and disease states. These include: the detection of viral, bacterial and protozoal agents; diagnosis and genetic analysis of inherited diseases such as β-thalassaemia, sickle cell disease, haemophilia, Tay-Sachs disease and many others; diagnosis and analysis of neoplastic disorders such as, chronic myelogenous leukaemia (CML), acute lymphocytic lymphoma (ALL), follicular lymphomas and various other cancers, including the detection of activated oncogenes; prenatal and pre-implantation diagnosis; and the development of genetic risk prediction. The PCR can greatly simplify diagnostic processes that were previously difficult to perform, particularly where the initial amounts of biological material were very limited. In other cases, PCR provides the only method available for detection and diagnosis. However, although simple in theory, the PCR technique remains, for routine clinical diagnostic purposes, currently in the domain of the specialist laboratory. This is because of its sensitivity to nucleic acid contamination from other sources that can cause misleading results. Procedures and precautions are being developed to minimize this problem and there is little doubt that, in many instances, the PCR will be the diagnostic method of choice within the next few years.