| Popis: |
This chapter discusses several methods for detection of nucleic acid. Two general amplification techniques—signal amplification and target amplification—have been used to improve the sensitivity of viral nucleic acid assays. The best DNA yields and diagnostic results are achieved when the nucleic acids are extracted from fresh specimens. Once the nucleic acids are purified and precipitated in ethanol, they are stable at -20°C for years. Nucleic acid sequence-based amplification and self-sustained sequence replication reactions are very similar; both these procedures are isothermal reactions that are patterned after the events that occur during retroviral transcription. Signal and target amplification systems have reduced the need for radioisotopes, reduced the turnaround times, and simplified testing protocols. Molecular methods are used to detect viruses that are difficult to cultivate in cell culture and, with the help of the amplification methods, molecular methods allow laboratories to detect viruses that are present in low numbers in clinical specimens (e.g., HIV and HSV in cases of suspected HSV encephalitis). However, molecular diagnostic methods have to be simpler, faster, and less expensive before their full potential is realized. |
