Many molecular assays use amplification to allow for the detection of the target or to ensure adequate copies of the target for identification. Amplification enables detection of the target even when sample size is small or when there are very few strands of DNA or RNA present. There are three types of amplification:
- Target Nucleic Acid Amplification
- The assay makes more copies of target nucleic acid before detection. Polymerase chain reaction (PCR) is the typical target amplification method.
- Signal Amplification
- The assay increases the number of labels and signal from labels. Target number remains unchanged. The HPV DNA assays discussed in this unit are examples of signal amplification methods.
- Probe or Probe Product Amplification
- The probe specific to the target or probe product is amplified only in the presence of a target (Target number remains unchanged). Ligase chain reaction is an example of a probe amplification method.