New molecular approaches for detecting viral genomes

The impact of a recently developed procedure, the polymerase chain reaction, is to be seen in all areas of molecular biology including virology and viral diagnostics. The power of the technique lies in its ability to amplify specific nucleic acid sequences from extremely low starting levels to amounts which can be readily detected, making it an obvious and attractive technique for the diagnosis of virus contamination. It has been developed for the detection of the hepatitis C virus genome in blood and blood products and it appears to be a more efficient marker for infectivity than the detection of anti-HCV antibodies. Considerable care must be taken in the use of PCR as a diagnostic technique because its exquisite sensitivity can easily give rise to false positives. Whilst PCR has an obvious role in safety testing of biologicals it will not be used in isolation but will complement other tests for infectivity and virus contamination.