The use of molecular biological techniques for the detection of human viral pathogens had modest beginnings more than 20 years ago and has evolved to include PCR assays for a comprehensive range of viral and bacterial agents of clinical significance. The traditional methods of virus detection by cultivation in cell cultures or direct detection by electron microscopy have largely been replaced by molecular techniques. These sensitive new techniques have facilitated provision of results in a timely manner and enabled the detection and typing of viruses that are not easily cultivated in standard cell lines.
The highly specific nature of molecular assays presents a number of challenges. Assays must be regularly monitored to ensure continued suitability to detect prevalent virus strains. Additionally there is a requirement for molecular diagnostic assays for the detection of emerging and re-emerging viruses and for agents for which commercial assays are not available.
However, the demands of increasing workloads with finite resources demand continual improvement and rationalisation of the PCR assays. Most of the conventional PCR assays have been replaced by real-time PCR assays, the manual sample extraction process has moved to automated platforms, and in the near future, robotic devices will complete the assays. Additionally individual PCR assays have been replaced by multiplex assays and a range of reaction chemistries have been evaluated. Synthetic control materials and improved amplicon contamination prevention strategies have been established.
Exciting developments such as whole genome sequence analysis may eventually replace some of these techniques, but for now the PCR assay remains an important tool in the diagnostic pathology laboratory.